Abstract: A field effect transistor having a doped region in the substrate immediately underneath the gate of the transistor and interposed between the source and drain of the transistor is provided. The doped region has a retrograde dopant profile such that the doping concentration immediately adjacent the gate is selected to allow for the formation of a channel when a threshold voltage is applied to the gate thereby eliminating the need for an enhancement doping step during formation of the transistor. The retrograde doping profile increases with the depth into the substrate which inhibits stray currents from traveling between the source and drain of the transistor in the absence of the formation of a channel as a result of voltage being applied to the gate of the transistor.

Abstract: A semiconductor memory device has a silicon substrate 10. A first embedded layer 11 is formed in the silicon substrate 10 under a p-well 18 in an area below a region where a drain 36 of a driver transistor 30 is located. The first embedded layer 11 makes a junction with the p-well 18. Also, the first embedded layer 11 is formed below an n-well 16 and contacts the n-well 16. When the drain 36 of the driver transistor 30 is at a voltage of 3V, &agr;-ray may pass through the p-well 18, the first embedded layer 11 and the silicon substrate 10. As a result, electron-hole pairs are cut. Due to the presence of the p-n junction that is formed by the p-well 18 and the first embedded layer 11, only electrons in the p-well 18 are drawn to the drain 36. As a result, a fall in the drain voltage of 3V is reduced. As a consequence, the device structure makes it difficult to destroy retained data.

Abstract: A semiconductor device has, in one embodiment, two wells of different conductivity types formed in a semiconductor substrate. The two wells are arranged to be adjacent to each other to form a junction therebetween. A field oxide film is formed to cover the junction at a main surface of the semiconductor substrate. Other field oxide films or field-shield isolation structures may be formed to isolate circuit elements from one another in the wells.

Abstract: A semiconductor substrate having a first conductivity type is first prepared. Then, a well region is formed in the substrate so as to have a second conductivity type opposite to the first conductivity type. Next, a first ion having the first conductivity type is implanted into the well region to form a region to be a first drain region having a first impurity density and into the substrate to form a region to be a first channel stopper region. Next, a second ion having the second conductivity type is implanted into the well to form a region to be a second channel stopper region and into the substrate to form a region to be a the second drain region having a second impurity density. Then, the respective ion implanted regions are thermally diffused to form the first drain region and the second channel stopper region in the well region and to form the second drain region and the first channel stopper region in the substrate.

Abstract: The present invention provides a method of manufacturing a semiconductor device, and a related method manufacturing an integrated circuit. In one embodiment, the method of manufacturing a semiconductor device includes creating a source/drain region between an electrode and an isolation structure located on a substrate. The method further includes implanting a dopant at a predetermined implant dopant concentration through an opening formed in a channel stop mask and located between the electrode and the isolation structure to form a channel stop between the source/drain region and the isolation structure.

Abstract: There is provided a semiconductor device in which improvement of drive capacity and miniaturization are made. A P-type transistor is composed of a surface channel type transistor so that a channel length is easily reduced. Thus, improvement of drive capacity and miniaturization are promoted. Further, since a gate insulating film is nitrided, reliability of the gate insulating film is improved and passing of boron contained in a p-type polycrystalline silicon gate electrode toward a channel region can be prevented. A step of forming the gate insulating film, a step of nitriding the gate insulating film, a step of performing thermal treatment using an inert gas, a step of forming a gate electrode on the gate insulating film, and a step of introducing a p-type impurity into the gate electrode are performed. Thus, a surface channel P-type transistor and a buried channel N-type transistor are constructed.

Abstract: A method for fabricating an SRAM device having a standard well tub, where an additional well tub is deposited within the standard well tub. In this manner, the dopant concentration is increased in the well area of the SRAM device, which increases both the isolation punchthrough tolerance and the SER immunity of the device. The additional well tub is deposited to a depth that is shallower than the standard well tub. The additional well tub is deposited using an ion implantation process using the same mask set as that used for the threshold voltage adjustment deposition. Thus, no additional mask layer is required to deposit the additional well tub, and the all of the expenses normally associated with an additional mask layer are avoided.

Abstract: An improved method of making CMOS surface channel transistors using fewer masking steps. In-situ doped poly silicon deposition can be used to reduce problems with poly depletion effects in transistor gates. In addition, using this method, the number of layers in each gate dielectric, the dielectric type, and dielectric thickness between n-channel and p-channel devices can be separately controlled. This method also allows the use of a lithography mask normally used to fabricate buried channel devices for use in fabricating surface channel devices, thus saving the manufacture of an additional mask.

Abstract: A method for fabricating a metal-oxide semiconductor (MOS) transistor. A substrate having a gate structure is provided. The method of the invention includes forming a liner spacer on each side of the gate structure and a low dopant density region deep inside the substrate. The low dopant density region has a lower dopant density than that of a lightly doped region of the MOS transistor. Then a interchangeable source/drain region with a lightly doped drain (LDD) structure and an anti-punch-through region is formed on each side of the gate structure in the low dopant density region. The depth of the interchangeable source/drain region is not necessary to be shallow.

Abstract: There is provided a method of fabricating a semiconductor device, including the steps of (a) forming first well regions in a semiconductor substrate in all regions in which high-voltage and low-voltage MOS transistors are to be formed, the semiconductor At e having a first conductivity and the first well regions having a second conductivity, (b) forming an isolation layer on the semiconductor substrate for isolating the first well regions from each other, (c) forming high-voltage well regions having a first conductivity and low-voltage well regions one of which has a first conductivity and another of which has a second conductivity, and (d) forming MOS transistors on the high-voltage and low-voltage well regions. The high-voltage and low-voltage well regions are formed with the isolation layer being used as a mark. The above-mentioned method makes it possible to form low-voltage and high-voltage MOS transistors on a common semiconductor substrate in the smallest number of fabrication steps.

Abstract: Method for producing an NMOS, PMOS or CMOS semiconductor device with reduced substrate current and increased device lifetime. A source-gate-drain device is fabricated having a moderately doped source region, a lightly doped source region, a gate or channel region, a lightly doped drain region, and a moderately doped drain region, arranged consecutively in that order, with the channel region adjacent to the gate having opposite electrical conductivity type to the electrical conductivity type of the source and drain regions. The source region and drain region are formed by ion implantation with ion kinetic energies of 40 keV or more, to increase the width and depth of charge carrier flow in these regions and to thereby reduce the substrate current associated with the device to less than one &mgr;Amp/&mgr;m.

Abstract: A voltage clamping circuit that protects integrated circuits having multiple separate power supply voltage terminals from damage when an ESD event causes excessive differential voltages between the multiple separate power supply voltage terminals. The voltage clamping circuit has two subgroups of Darlington connected clamping transistors. The first subgroup of Darlington connected clamping transistors is connected between the first power supply voltage terminal and the second power supply voltage terminal. If the differential voltage exceeds the first clamping voltage level, the first subgroup of Darlington connected clamping transistors turn on and restore the first differential voltage to a level less than the first clamping voltage level. The second subgroup of Darlington connected clamping transistors connected between the second power supply terminal and the first power supply terminal.

Abstract: A semiconductor device having two or more types of separation oxide film are formed on the substrate of the semiconductor device by different methods so as to correspond with element types formed on the same semiconductor substrate. The method for producing the semiconductor device comprises a first separation oxide film formation process, and a second separation oxide film formation process. In the first separation oxide film formation process, a first mask layer is formed on the semiconductor substrate, the first mask layer of the element separation region of the logic element is selectively removed and the semiconductor substrate in the region area selectively oxidized. In second separation oxide film formation process, the remaining first mask layer is removed, a second mask layer is formed, the second mask layer of the element separation region of DRAM elements is then selectively removed, and the semiconductor substrate of the region is selectively oxidized.

Abstract: A high-voltage device. A substrate has a first conductive type. A first well region with the first conductive type is located in the substrate. A second well region with the second conductive type is located in the substrate but is isolated from the first well region. Several field oxide layers are located on a surface of the second well region. A shallow trench isolation is located between the field oxide layers in the second well region. A first doped region with the second conductive type is located beneath the field oxide layers. A second doped region with the first conductive type is located beneath the shallow trench isolation in the second well region. A third well region with the first conductive type is located in the first well region and expands from a surface of the first well region into the first well region. A gate structure is positioned on the substrate between the first and the second well regions and covers a portion of the first, the third well regions and the field oxide layers.

Abstract: A method for fabricating a semiconductor device comprises implantating and diffusing a first well in a semiconductor substrate. A second well is implantated and diffused in the first well. A third well is implantated in the second well and a MOS transistor is formed in the third well.

Abstract: In a semiconductor memory device, first and second impurity regions of a second conductivity are provided as wells in a semiconductor substrate of a first conductivity. Outside of the first and second impurity regions, third impurity regions of the first conductivity are provided as wells in the substrate. Fourth impurity regions of the first conductivity are provided as wells in the first impurity regions. The first impurity regions each have an impurity concentration which gradually decreases with increasing depth below the top surface of the semiconductor substrate, and the fourth impurity regions have at least two impurity concentration peaks below the top surface of the semiconductor substrate. A memory cell can be reliably erased by forming a retrograde pocket well for a memory cell array, and a diffusion well surrounding the pocket well, thus maintaining a high breakdown voltage between the pocket well and the substrate.

Abstract: An electro-static discharge (ESD) circuit of a semiconductor device, a structure thereof and a method for fabricating the ESD structure are provided. In the ESD circuit, a gate electrode and a drain region of a MOS transistor are connected to an electrical signal pad, and a Zener diode is connected to a source region of the MOS transistor. A threshold voltage of the MOS transistor is higher than an operating voltage of an internal circuit and lower than a drain junction breakdown voltage of a MOS transistor constituting the internal circuit. Also, instead of using a Zener diode for each signal pad, a common diode having a maximized junction area can be shared by a plurality of signal pads.

Abstract: A method for incorporating an ion implanted channel stop layer under field isolation for a twin-well CMOS process is described in which the layer is placed directly under the completed field isolation by a blanket boron ion implant over the whole wafer. The channel stop implant follows planarization of the field oxide and is thereby essentially at the same depth in both field and active regions. Subsequently implanted p- and n-wells are formed deeper than the channel stop layer, the n-well implant being of a sufficiently higher dose to over compensate the channel stop layer, thereby removing it's effect from the n-well. A portion of the channel stop implant under the field oxide adjacent the p-well provides effective anti-punchthrough protection with only a small increase in junction capacitance. The method is shown for, and is particularly effective in, processes utilizing shallow trench isolation.

Abstract: There is disclosed a method for manufacturing a semiconductor integrated circuit of triple well structure, comprising the steps of forming an N-well, a P-well and a device isolation region in an N-type silicon substrate, thereafter forming a silicon oxide film on the whole surface of the silicon substrate by a thermal oxidation, forming a resist mask covering a region in which the silicon oxide film is required, ion-implanting a P-type impurity using the resist mask as a mask and with an implantation energy enough to allow the ion-implanted impurity to reach a bottom of the N-well and the P-well, so as to form a buried impurity layer, thereafter removing the silicon oxide film not covered with the resist mask by an etching, then removing the resist mask, and conducting a thermal oxidation on the whole surface of the silicon substrate so that a relatively thick gate oxide film is formed on a region which was covered with the resist mask, and a relatively thin gate oxide film is formed on a region which was not

Abstract: A method for fabricating a high vltage device with double diffusion structure provides a pad oxide layer on a silicon substrate. A silicon nitride layer is formed and patterned to expose isolation regions. A first mask covers the partial isolation regions spaced from the silicon nitride layer. A well region is formed underlay the silicon nitride layer. A second mask covers the partial isolation region spaced from the silicon nitride layer and the partial silicon nitride layer. First doped regions are formed underlay the partial silicon nitride layer. Then the isolation regions are formed partially on the first doped regions. Next, a third mask covers the pad oxide layer and the partial isolation regions and second doped regions are formed spaced from the first doped regions and below the isolation regions. A gate is formed and located between the first doped regions and a spacer on a side-wall thereof. Third doped regions are formed in the first doped regions.

Abstract: A method of forming a pillar CMOS FET device, especially an inverter, and the device so formed is provided. The method includes forming abutting N wells and P wells in a silicon substrate and then forming N+ and P+ diffusions in the P and N wells respectively. A unitary pillar of the epitaxial silicon is grown on the substrate having a base at the substrate overlying both the N and P wells and preferably extending at least from said N+ diffusion to said P+ diffusion in said substrate. The pillar terminates at a distal end. An N well is formed on the side of the pillar overlying the N well in the substrate and a P well is formed on the side of the distal end of the pillar overlying the P well on the substrate and abuts the N well in the pillar. A P+ diffusion is formed in the N well in the pillar adjacent the distal end and a N+ diffusion is formed in the P well in the pillar adjacent the distal end.

Abstract: An MOS device is provided using indium as a threshold adjust implant in the channel regions of an NMOS device and/or in the conductive gate overlying the channel region in a PMOS device. Indium ions are relatively immobile and achieve location stability in the areas in which they are implanted. They do not readily segregate and diffuse in the lateral directions as well as in directions perpendicular to the silicon substrate. Placement immobility is necessary in order to minimize problems of threshold skew and gate oxide thickness enhancement. Additionally, it is believed that indium atoms within the channel region minimize hot carrier effects and the problems associated therewith.

Abstract: Methods of forming field effect transistors.

Abstract: An array of P-channel memory cells is separated into independently programmable memory segments by creating multiple, electrically isolated N-wells upon which the memory segments are fabricated. The methods for creating the multiple, electrically isolated N-wells include p-n junction isolation and dielectric isolation.

Abstract: The invention provides a method for forming a ROM cell surface implant region using a PLDD implant. A semiconductor structure is provided comprising a substrate having isolation structures thereon, which separate and electrically isolating a first area having a P-well formed in the substrate and a gate over the substrate, a second area having a N-well formed in the substrate and a gate over the substrate, and a third area having P-well and buried N+ regions formed in the substrate with second isolation structures overlying the buried N+ regions. A photoresist mask is formed exposing the first area, and impurity ions are implanted to form n-type lightly doped source and drain regions. The photoresist mask is removed and a new (PLDD/ROM) photoresist mask is formed exposing the second area and the third area. Impurity ions are implanted to simultaneously form p-type lightly doped source and drain regions and a ROM cell surface implant region region. The PLDD/ROM photoresist mask is then removed.

Abstract: A twin-well CMOS integrated circuit device includes an n-well region and a p-well region. Each of the n-well and p-well region includes spaced-apart regions which serve as drain and source regions, a channel region between the spaced-apart regions, a shallow trench isolation structure contiguous with one of the spaced-apart regions, and a doped diffused region extending from the surface of the well region, around and underneath the trench isolation structure, to a region beneath the contiguous spaced-apart region.

Abstract: A semiconductor device comprising a dual polysilicon gate structure in which the P type polysilicon gate is connected with the N type polysilicon gate by a bilayer conductive wiring structure without any contact, thereby significantly contributing to high integration, and a method for fabricating the semiconductor device such that the production yield is improved.

Abstract: Methods are described to prevent the inherent latchup problem of CMOS transistors in the sub-quarter micron range. Latchup is avoided by eliminating the low resistance between the Vdd and Vss power rails caused by the latchup of parasitic and complementary bipolar transistor structure that are present in CMOS devices. These goals have been achieved without the use of guard rings by using a deep n-well to disconnect the pnp collector to npn base connection of two parasitic bipolar transistors, and by using a buried p-well to disconnect the npn collector to pnp base connection of those same two parasitic transistors. Further, the deep n-well is shorted to a supply voltage Vdd, and the buried p-well is shorted to a reference voltage Vss via both the P substrate and a P+ ground tab. The proposed methods do not require additional mask or processes.

Abstract: A method of fabricating a CMOS transistor using Si—B layer to form a source/drain extension junction is disclosed. The fabrication includes the steps as follows; First, a p-type semiconductor substrate and an n-well region are provided. Afterwards, a shallow trench isolation (STI) is formed into the p-type semiconductor substrate and the n-well region, thereby forming a plurality of active regions therebetween. A channel is formed into the p-type semiconductor substrate and the n-well region. Then, a PMOSFET gate pattern and an NMOSFET gate pattern are formed over the p-type semiconductor substrate and the n-well region. A first defined photoresist layer is formed over the n-well region. Afterwards, the n−-type dopant is implanted into the p-type semiconductor substrate to form an n−-type lightly doped source/drain. Then the first defined photoresist layer is removed. A first dielectric layer is deposited over the p-type semiconductor substrate and the n-well region.

Abstract: A method for fabricating a BiCDMOS device where bipolar, CMOS and DMOS transistors are formed on a single wafer is provided. A semiconductor region of a second conductivity type is formed on a semiconductor substrate of a first conductivity type. Well regions of first and second conductivity types are formed within the semiconductor region. Then, an oxidation passivation layer pattern defining a region where a pad oxide layer and a field oxide layer are to be formed is formed on a surface of the substrate where the well regions have been formed. Impurity ions of the first conductivity type are implanted into the entire surface of a region where the field oxide layer is to be formed, using the oxidation passivation layer pattern as an ion implantation mask. An ion implantation mask pattern defining a field region of the second conductivity type is formed on the substrate where the oxidation passivation layer has been formed.

Abstract: A method for forming a field effect transistor (FET) is disclosed which includes forming an isolation region in a substrate of semiconductor material, anisotropically etching the substrate such that a sidewall spacer region of semiconductor material remains on a sidewall of the isolation region as a device region of the FET. The isolation region may then be recessed such that, after gate conductor deposition, the central channel region of the device region is enclosed by the gate conductor. A dopant concentration in at least one of the central portion of the device region or regions flanking the central portion are then altered to form source-drain regions having a first dopant type and a channel region having a second dopant type opposite the first dopant type.

Abstract: Systems and methods are described for fabricating semiconductor gate oxides of different thicknesses. Two methods for forming gate oxides of different thicknesses in conjunction with local oxidation of silicon (LOCOS) are disclosed. Similarly, two methods for forming gate oxides of different thicknesses in conjunction with shallow trench isolation (STI) are disclosed. Techniques that use two poly-silicon sub-layers of substantially equal thickness and techniques that use two poly-silicon sub-layers of substantially unequal thickness are described for both LOCOS and STI. The systems and methods provide advantages because gate uniformity and quality are improved, the processes and resulting devices are cleaner, and there is less degradation of carrier mobility.

Abstract: A method of developing a transistor, such as a complimentary MOS (CMOS) transistor, that includes lightly doped drain (LDD) regions which uses disposable spacers, and includes the step of adding an oxide spacer etch after a disposable nitride spacer removal and between source/drain implant and LDD implant. Because of this additional step, an ultra shallow LDD implant can be achieved. Moreover, uniformity of the depth of the junction is improved as the non-uniformity of the screen/liner oxide is eliminated.

Abstract: A method of fabricating a dual gate. A first conductive type region and a second conductive type region isolated by an isolation structure is provided. A polysilicon layer is formed on the first and the second conductive type regions. A diffusion layer containing second type conductive ions is formed on a second part of the polysilicon layer which covers the second conductive type region. First conductive ions are implanted into a part of the first conductive region which covers the first conductive type region. A first thermal process is performed. A metal layer is formed, and a second thermal process is performed, so that the metal layer is transformed into a metal silicide layer. A dielectric layer is formed on the metal layer. The dielectric layer, the metal silicide layer, diffusion layer, and the polysilicon layer are patterned to form a dual gate.

Abstract: A method of fabricating a CMOS semiconductor device is provided, which decreases the number of necessary photolithography processes for forming the LDD and pocket structures. A first pair of doped regions of a first conductivity type are formed in a first section of a semiconductor substrate and a second pair of doped regions of the first conductivity type are formed in a second section thereof. Then, a third pair of doped regions of a second conductivity type are formed in the first pair of doped regions and a fourth pair of doped regions of the second conductivity type are formed in the second pair of doped regions. Thereafter, an impurity of the second conductivity type is selectively ion-implanted into the first section while covering the second section with a mask, thereby forming a fifth pair of doped regions of the second conductivity type from the first pair of remaining doped regions.

Abstract: A method of forming a twin well includes the steps of: forming a field oxide layer on a semiconductor substrate to define active regions of a device, and forming a first mask which exposes a predetermined active region of the semiconductor substrate; ion-implanting a first conductivity type impurity into the exposed region of the semiconductor substrate using the first mask as an ion implantation mask, to form a first well; ion-implanting a second conductivity type impurity to penetrate the first mask, to form a buried region which is self-aligned with the first well and comes into contact with the bottom of the field oxide layer; removing the first mask, and forming a second mask which is to expose the first well of the semiconductor substrate; and ion-implanting a second conductivity impurity into the exposed region of the semiconductor substrate to levels deeper and shallower than the buried region using the second mask as an ion implantation mask, to form a second well including the buried region.

Abstract: A method of forming a pillar CMOS FET device, especially an inverter, and the device so formed is provided. The method includes forming abutting N wells and P wells in a silicon substrate and then forming N.sup.+ and P.sup.+ diffusions in the P and N wells respectively. A unitary pillar of the epitaxial silicon is grown on the substrate having a base at the substrate overlying both the N and P wells and preferably extending at least from said N.sup.+ diffusion to said P.sup.+ diffusion in said substrate. The pillar terminates at a distal end. An N well is formed on the side of the pillar overlying the N well in the substrate and a P well is formed on the side of the distal end of the pillar overlying the P well on the substrate and abuts the N well in the pillar. A P.sup.+ diffusion is formed in the N well in the pillar adjacent the distal end and a N.sup.+ diffusion is formed in the P well in the pillar adjacent the distal end.

Abstract: The present invention includes forming gate structures having a nitride cap on the substrate. An ion implantation is used to dope ions into the substrate to form the lightly doped drain (LDD) structures. An oxide layer is formed on the gate structures. Subsequently, the oxide layer is etched back to form oxide spacers on the side walls of the gate structures. Next, an ion implantation with a tilted angle relative to the normal line of the substrate is used. The tilted angle is about 30 to 90 degrees respect to the substrate. The ions pass through the spacers, gate oxide and into the substrate under a portion of the gate by controlling the energy of the ion implantation. The spacers also doped with ions during the implantation. The energy of the ion implantation is about 5 to 150 KeV, and the dosage of the ion implantation is about 5E12 to 2E15 atoms/cm.sup.2. The cap silicon nitride layer is then removed.

Abstract: Disclosed is a manufacturing method of semiconductor device which can simplify the manufacturing procedures for transistors with different gate insulation film thickness in the same substrate. According to the present invention, a manufacturing method for semiconductor device having NMOS and PMOS transistors with gate insulation films of different thickness from each other, is formed by the following processes. First, a semiconductor substrate in which a low voltage NMOS transistor region, a high voltage NMOS transistor region, a low voltage PMOS transistor region, and a high voltage PMOS transistor region are defined by isolation films, is provided. Next, a N well is formed in the low and high voltage PMOS transistor regions and threshold voltage adjustment ions for high voltage PMOS transistor are then implanted into the N well.

Abstract: Semiconductor-on-insulator (SOI) devices are fabricated by forming first and second semiconductor layers of opposite conductivity types, at a first face of a substrate. An insulating layer is formed on the first and second semiconductor layers. A trench is formed through the insulating layer extending between the first and second semiconductor layers and extending into the substrate. A portion of the substrate is removed from a second face which is opposite the first face, to define respective first and second active regions on the respective first and second semiconductor layers.

Abstract: A method of making semiconductor devices which enables control of the impurity concentration and fine patterning by making removal of residual stress due LOCOS oxidation compatible with the formation of deep wells. A selective oxide layer is formed for separating element regions on a principal plane of a semiconductor substrate, for example, a p.sup.- -type silicon substrate 1. A mask is formed (for example photoresist 47) on the surface including the selective oxide layer and impurities (for example phosphorous) of a conductivity type opposite that of the semiconductor substrate are introduced via an opening in the mask. Then the selective oxide film is annealed by a high-temperature treatment while a deep well (for example n-type deep well 50) is formed by introducing the impurities.

Abstract: The present invention relates to a method for fabricating semiconductor devices having triple wells, the present invention has an effect as follows. The present invention provides carrying out N-well and P-well and R-well ion implantation using a mask for implanting two wells after forming an element isolation oxide film, defining an accurate well region by forming wells having an accurate profile due to activating impurity ions in accordance with the thermal process, and improving the punch characteristic between a well and a well.

Abstract: A semiconductor device include: a substrate of a conductivity type; a first well provided in the substrate and of the same conductivity type as the conductivity type of the substrate; a second well provided in the substrate and of an opposite conductivity type to the conductivity type of the substrate; and a buried well provided at a deep position in the substrate and of the opposite conductivity type to the conductivity type of the substrate. A buried well of the same conductivity type as the conductivity type of the substrate is further provided so as to be in contact with at least a part of a bottom portion of the first well so that the first well is at least partially electrically connected to the substrate.

Abstract: A method for forming planarized isolation by combining LOCOS and STI isolation processes is described. A first nitride layer is deposited over a pad oxide layer on the surface of a semiconductor substrate. The first nitride layer and pad oxide layer are etched through where they are not covered by a mask to provide openings where the surface of the semiconductor substrate is exposed wherein there is at least one wide opening and one narrow opening. A second nitride layer is deposited over the substrate and etched back to leave spacers on the sidewalls of the openings wherein the narrow opening is filled by the spacers. The exposed semiconductor substrate within the wide opening is oxidized wherein a field oxide region is formed within the wide opening. A portion of the first nitride layer and spacers is etched away whereby the semiconductor substrate within the narrow opening is exposed. A trench is etched into the semiconductor substrate where it is exposed within the narrow opening.

Abstract: An IC comprises a tub of a first conductivity type, at least one transistor embedded in the tub, and a first pair of isolating regions defining therebetween a tub-tie region coupled to the tub. The tub-tie region comprises a cap portion of the first conductivity type and an underlying buried pedestal portion of a second conductivity type. At least a top section of the pedestal portion is surrounded by the cap portion so that a conducting path is formed between the cap portion and the tub. In a CMOS IC tub-ties of this design are provided for both NMOS and PMOS transistors. In a preferred embodiment, the cap portion of each tub-tie comprises a relatively heavily doped central section and more lightly doped peripheral sections, both of the same conductivity type.

Abstract: Over the principal surface of a semiconductor substrate body containing an impurity of a predetermined conduction type, there is formed an epitaxial layer which contains an impurity of the same conduction type as that of the former impurity and the same concentration as the designed one of the former impurity. After this, there are formed a well region which has the same conduction type as that of said impurity and its impurity concentration gradually lowered depthwise of said epitaxial layer. The well region is formed with the gate insulating films of MIS.FETs.

Abstract: A method of forming a trench capacitor over a semiconductor substrate comprises the following steps. First, a nitride layer is formed on the substrate. Then, a first oxide layer is formed on the nitride layer. Next, the first oxide layer and the nitride layer are etched to expose a portion of the surface of the substrate. An etching back step is performed to etch the nitride layer to pull back the sidewalls of the nitride layer. Next, the second oxide layer is formed above the first oxide layer, the nitride layer and the substrate. An etching step is done to form the trench structure on the substrate by using the first oxide layer as a mask. Then, a wet etching step is performed to remove the first oxide layer and the second oxide layer. Next, a doping step is done to form the doped region in the trench structure. A dielectric layer is then formed above the doped region. A conducting layer is formed on the dielectric layer, wherein the conducting layer is coupled with a drain.

Abstract: The preferred embodiment of the present invention overcomes the limitations of the prior art and provides a device and method to increase the latch-up immunity of CMOS devices by forming implants at the well edges. The preferred method uses hybrid resist to form these implants at the edges of the N-wells and/or P-wells. The implants reduce the lifetime of minority carriers in the parasitic transistor, and hence reduce the gain of the parasitic transistor. This reduces the propensity of the CMOS device to latch-up. The preferred embodiment method allows these implants to be formed without requiring additional masking steps over prior art methods. Furthermore, the preferred method for forming the implants results in implants that are self aligned to the edges of the wells.

Abstract: A method of improving latch-up immunity and interwell isolation in a semiconductor device is provided. In one embodiment, an implant mask which has a variable permeability to implanted impurities is formed on the surface of a substrate having a first dopant region. A first portion of the implant mask overlies a first portion of the first dopant region. The structure is subjected to high energy implantation which forms a heavily doped region. A first portion of the heavily doped region is located along the lower boundary of the first dopant region. A second portion of the heavily doped region which extends along a side boundary of the first dopant region is formed by impurity ions which pass through the first portion of the implant mask. The heavily doped region improves latch-up immunity and interwell isolation without degrading threshold voltage tolerance.

Abstract: In order to suppress a reverse short-channel effect, a plurality of dummy gates, wherein gate electrodes are respectively to be formed, are formed in selective regions on the substrate. Further, the regions wherein first conductive type elements are to be formed are masked. Thereafter, a first conductive type well by ion planting a first conductive type impurity is formed. Further, a second conductive type source and drain region is formed by ion planting a second conductive type impurity. The resist covering the regions, wherein the first conductive type elements are to be formed, are removed. Following this, regions wherein second conductive type elements are to be formed, are masked by a resist. Further, a second conductive type well is formed by ion planting a second conductive type impurity. A first conductive type source and drain region is formed by ion planting a first conductive type impurity.