Abstract: An integrated circuit (IC) is formed on a substrate. The IC has a first well having a first dopant concentration that includes a second conductivity low-voltage transistor. The IC also has a second well having a dopant concentration equal to the first dopant concentration that includes a first conductivity high-voltage transistor. In addition, the IC has a third well having a second dopant concentration of an opposite type than the first well that includes a first conductivity low-voltage transistor. The first conductivity low-voltage transistor and the second conductivity low-voltage transistor are created without a threshold voltage (Vt) implant.

Abstract: A lithography method for plating sub-100 nm narrow trenches, including providing a thin undercoat dissolution layer intermediate a seed layer and a resist layer, wherein the undercoat dissolution layer is relatively completely cleared off the seed layer by the developer solution such that the sides of the narrow trench will be generally vertical, particularly at the base of the narrow trench, thus facilitating plating the narrow trench with a high magnetic moment material.

Abstract: A method to provide a triple well in an epitaxially based CMOS or B:CMOS process comprises the step of implanting the triple well prior to the epitaxial deposition.

Abstract: A method for fabricating a triple well in a semiconductor device, includes the steps of forming a first well of a first conductive type with a first concentration lower than a first target concentration, wherein the first concentration is the minimum dose capable of isolating neighboring wells each other and forming a second well of a second conductive type with a second concentration higher than a second target concentration, wherein the second well includes a first region surrounded by the first well and a second region isolated from the first region by the first well.

Abstract: A method for forming a lateral SCR device for on-chip ESD protection in shallow-trench-isolation CMOS process is provided. In the present lateral SCR device, the shallow trench isolation among the current conduction path of the lateral SCR device is removed and instead of a dummy gate. Thereby, the SCR device has a narrower anode-to-cathode spacing, and then the lateral SCR device can be turned on more quickly to protect the CMOS IC's in ESD events. Additionally, the silicon area of the substrate occupied by the lateral SCR device is also saved. This method for forming a lateral SCR device without shallow-trench-isolation regions in its current path can be fully process-compatible to general CMOS technologies by only changing layout patterns in the mask layers.

Abstract: A varactor diode having a first electrode comprising a well region of a first conductivity type in a substrate, a second electrode comprising a first plurality of diffusion regions of a second conductivity type abutting isolation regions disposed in said well region, and a second plurality of diffusion regions of said first conductivity type extending laterally from portions of said first plurality of diffusion regions not adjacent said isolation regions and having a dopant concentration greater than that of said first plurality of diffusion regions. The varactor has a tunability of at least approximately 3.5 in a range of applied voltage between approximately 0V to 3V, an approximately linear change in capacitive value in a range of applied voltage between approximately 0V to 2V, and a Q of at least approximately 100 at a circuit operating frequency of approximately 2 GHz.

Abstract: The present invention relates to the formation of trench isolation structures that isolate active areas and a preferred doping in the fabrication of a CMOS device with a minimized number of masks. Ions of a P-type dopant are implanted into a semiconductor substrate having therein a P-well and an N-well. Each of the N-well and P-well has therein a trench. The ions of the P-type dopant are implanted beneath each of the trenches in the P-well and the N-well to create a first P-type dopant concentration profile in the semiconductor substrate, wherein the P-well and the N-well are substantially unimplanted by the ions of the P-type dopant in active areas adjacent to the respective trenches therein. A second implanting ions of a P-type dopant is made into the semiconductor substrate. The second implanting is beneath each of the trenches in the P-well and the N-well to form a second P-type dopant concentration profile.

Abstract: A method for fabricating a CMOS transistor is disclosed. The present invention provides a method for producing a CMOS transistor having enhanced performance since a short channel characteristic and operation power can be controlled by the duplicate punch stop layer of the pMOS region and the operation power of the nMOS is also controlled by dopant concentration of the duplicated LDD region combined by the first LDD region and the second LDD region.

Abstract: A semiconductor device with dynamic threshold transistors includes a complex element isolation region composed of a shallow element isolation region made of shallow trench isolation and deep element isolation regions provided on both sides of the shallow element isolation region. Since the shallow element isolation region is made of the shallow trench isolation, Bird's beak in the shallow element isolation region is small. This prevents off leakage failure due to stress caused by the bird's beak. The deep element isolation region has an approximately constant width which allows the complex element isolation region to be wide.

Abstract: Dynamic Random Access Memory (DRAM) cells are formed in a P well formed in a biased deep N well (DNW). PMOS transistors are formed in N wells. The NMOS channels stop implant mask is modified not to be a reverse of the N well mask in order to block the channels stop implant from an N+ contact region used for DNW biasing. In DRAMs and other integrated circuits, a minimal spacing requirement between a well of an integrated circuit on the one hand and adjacent circuitry on the other hand is eliminated by laying out the adjacent circuitry so that the well is located adjacent to a transistor having an electrode connected to the same voltage as the voltage that biases the well. For example, in DRAMs, the minimal spacing requirement between the DNW and the read/write circuitry is eliminated by locating the DNW next to a transistor precharging the bit lines before memory accesses. One electrode of the transistor is connected to a precharge voltage.

Abstract: Methods are disclosed for manufacturing semiconductor devices with silicide metal gates, wherein a single-step anneal is used to react a metal such as cobalt or nickel with substantially all of a polysilicon gate structure while source/drain regions are covered. A second phase conductive metal silicide is formed consuming substantially all of the polysilicon and providing a substantially uniform work function at the silicide/gate oxide interface.

Abstract: A semiconductor device and method of manufacturing the semiconductor device including a semiconductor substrate of a first conductivity type. A scribe lane area formed in the substrate to define chip formation areas. A deep well area formed in each chip formation area. The deep well area has a second conductivity type which is opposite the first conductivity type. Also, at least one well area is formed within the deep well area.

Abstract: A new process integration method is described to form heavily doped p+ source and drain regions in a CMOS device. After defining the p- and n-well regions on a semiconductor substrate, gate silicon dioxide is deposited and nitrided in a nitrogen-containing atmosphere. Poly-silicon is then deposited and the two NMOS and PMOS gates are formed. For the p+ doping of the poly-silicon gate and S/D regions around the PMOS gate, B+ ions are then implanted. Cap dielectric layer comprising silicon dioxide is then deposited, followed by dopant activation with high temperature rapid thermal annealing. The cap dielectric layer is then used as resist protective film; it is removed from those areas of the chip that would require formation of electrical contacts. Silicide electrical contacts are then formed in these areas.

Abstract: A semiconductor device is disclosed. The device includes a semiconductor region and P-type and N-type diffusion layers formed in the semiconductor region. The semiconductor region includes a germanium low-concentration region containing germanium of low concentration and a germanium high-concentration region containing germanium of high concentration. A boundary region between the P-type and N-type diffusion layers lies in the germanium high-concentration region. A silicide film is formed to extend from the P-type diffusion layer over to the boundary region and the N-type diffusion layer.

Abstract: A method for fabricating source/drain devices. A semiconductor substrate is provided with a gate formed thereon, a first doped area is formed on a first side of the gate on the semiconductor substrate, and a second doped area is formed on a second side of the gate on the semiconductor substrate in a manner such that the second doped area is separated from the gate by a predetermined distance. A patterned photo resist layer is formed on the semiconductor substrate having an opening on the second side, the exposed gate less than half the width of the gate. The semiconductor substrate is implanted and annealed to form a dual diffusion area on the second side of the gate using the patterned photo resist layer as a mask.

Abstract: A device comprising: a layer of gate oxide on a surface of the semiconductor substrate; a gate electrode formed on the surface of the gate oxide, the gate electrode having a drain side; a p-well implanted within a semiconductor substrate under the gate electrode; an n-well implanted in the p-well on the drain side; an n+ source region in the p-well outside of the n-well; an n+ drain region within the substrate inside the n-well; and lightly doped regions extending respectively from the source and drain regions toward the gate electrode.

Abstract: A semiconductor device comprises a semiconductor substrate, a p-type well formed in the semiconductor substrate, an n-type well formed in the semiconductor substrate and positioned contiguous to the p-type well, an n-type diffused region formed in the p-type well, and a p-type diffused region formed in the n-type well, wherein a corner C1 having the p-type well on the inside is present in a part of the boundary pattern between the p-type well and the n-type well. At least one of the two sides defining the corner C1 extends from a top of the corner to the n-well by a predetermined width d over a predetermined length. The particular structure permits suppressing generation of a difference in a well isolation punch-through voltage between the corner and the straight portion of the well boundary of the semiconductor device, making it possible to provide a fine device structure while ensuring a desired well isolation punch-through voltage without relaxing a design rule.

Abstract: This invention relates to a CMOSFET 10 in which a p-type gate electrode 32a and an n-type gate electrode 32b are formed on a silicon substrate 12. The p-type gate electrode 32a comprises, in order, a p-type polycrystalline silicon layer 22a and a tungsten silicide layer 26a. The n-type gate electrode 32b comprises, in order, an n-type polycrystalline silicon layer 22b and a tungsten silicide layer 26b. A carbon-containing polycrystalline silicon layer 24, which is an impurity thermal diffusion prevention layer to suppress the interdiffusion of impurities, is provided between the p-type polycrystalline silicon layer 22a and the tungsten silicide layer 26a.

Abstract: A method of forming retrograde n-wells and p-wells. A first mask is formed on the substrate and the n-well implants are carried out. Then the mask is thinned, and a deep p implant is carried out with the thinned n-well mask in place. This prevents Vt shifts in FETs formed in the n-well adjacent the nwell-pwell interface. The thinned mask is then removed, a p-well mask is put in place, and the remainder of the p-well implants are carried out.

Abstract: A semiconductor device and a method for constructing a semiconductor device is disclosed. A deep trench isolation structure (108) is formed proximate a surface of a semiconductor substrate (106). A deep trench plug (122) layer is deposited within the deep trench isolation structure (108). A shallow trench isolation structure (130) is formed where the deep trench isolation structure (108) meets the surface of the semiconductor substrate (106). A shallow trench plug layer (133) is deposited within the shallow trench isolation structure (130).

Abstract: An object of the invention is to suppress degradation of the effective isolation width between a well and a diffusion layer caused by impurity ion implantation for forming the well performed at a predetermined incident angle. A well is formed by performing impurity ion implantation twice: first impurity ion implantation from a first direction at predetermined incident angle, acceleration voltage and dose; and second impurity ion implantation from a second direction different from the first direction by 180 degrees in a plan view at the same incident angle, acceleration voltage and dose as those in the first impurity ion implantation.

Abstract: A method is provided for manufacturing a semiconductor device that can reduce the number of steps in manufacturing a triple-well that includes multiple ion implantation steps and heat treatment steps.

Abstract: A dual-gate CMOS semiconductor device and a manufacturing method therefor suppressing mutual diffusion of P type impurities and N type impurities in a gate electrode are provided. This invention is comprised of an NMOS part 103 and a PMOS part 104 formed on a semiconductor substrate; a polycrystalline silicon layer formed on the NMOS part 103 and the PMOS part 104 and consisting of an N type impurity containing polycrystalline silicon layer 106 and a P type impurity containing polycrystalline silicon layer 107; and a first conductive layer 108 formed on the polycrystalline silicon layer so as to include a groove region 120, in which the first conductive layer is not formed, on a predetermined region including a boundary between the N type impurity containing polycrystalline silicon layer 106 and the P type impurity containing polycrystalline silicon layer 107.

Abstract: A modified STI process is provided comprising forming a first polysilicon layer over a substrate. Forming a trench through the first polysilicon layer and into the substrate, and filling the trench with an oxide layer. Depositing a second polysilicon layer over the oxide, such that the bottom of the second polysilicon layer within the trench is above the bottom of the first polysilicon layer, and the top of the second polysilicon layer within the trench is below the top of the first polysilicon layer. The resulting structure may then be planarized using a CMP process. An alignment key may be formed by selectively etching the oxide layer. A third polysilicon layer may then be deposited and patterned using photoresist to form a gate structure. During patterning, exposed second polysilicon layer is etched. An etch stop is detected at the completion of removal of the second polysilicon layer. A thin layer of the first polysilicon layer remains, to be carefully removed using a subsequent selective etch process.

Abstract: A CMOS transistor is formed on a single crystal silicon substrate. Active regions are formed on the substrate, including an nMOST active region and a pMOST active region. An epitaxial layer of undoped silicon is formed over the active regions. Out-diffusion from the underlying active regions produces dopant densities within the epitaxial layer one, or more, orders of magnitude lower than dopant densities within the underlying active regions. In a preferred embodiment, the epitaxial layer is counter doped by implanting ions of the opposite type to those within the underlying active region. Counter doping further reduces the dopant density, to reduce the threshold voltage further.

Abstract: A process for fabricating CMOS devices, featuring a channel region comprised with a strained SiGe layer, has been developed. The process features the selective growth of a composite silicon layer on the top surface of N well and P well regions. The composite silicon layer is comprised of a thin, strained SiGe layer sandwiched between selectively grown, undoped silicon layers. The content of Ge in the SiGe layer, between about 20 to 40 weight percent, allows enhanced carrier mobility to exist without creation of silicon defects. A thin silicon dioxide gate insulator is thermally grown from a top portion of the selectively grown silicon layer, located overlying the selectively grown SiGe layer.

Abstract: The dynamic random access memory (DRAM) cells in a semiconductor chip are isolated from the peripheral circuitry by forming the DRAM cells directly in the substrate while the peripheral and other functional circuits are formed in wells that are isolated from the substrate. In addition to providing isolation, the placement of the DRAM cells also reduces the leakage current in the cells, thereby increasing the time that a DRAM cell can hold a charge without being refreshed.

Abstract: A method is provided for processing a semiconductor topography. In particular, a method is provided for forming wells of opposite conductivity type using a single patterned layer. In addition, the method may include forming a silicon layer having first and second portions of opposite conductivity type. The formation of the silicon layer may include the use of the single patterned layer or an additional patterned layer. In addition, the method may include forming channel dopant regions within the wells of opposite conductivity type. The formation of such channel dopant regions may be incorporated into the method using the one or two patterned layers used for the formation of the wells and doped silicon layer. Such a method may include introducing impurities at varying energies and doses to compensate for the introduction of subsequent impurities. As such, the method may form a dual gate transistor pair, including n-channel and p-channel transistors.

Abstract: A process of manufacturing a semiconductor device having a dual gate CMOS transistor in which an nMOS transistor in the dual gate CMOS transistor is formed by the steps of: (a) forming a gate insulating film and a silicon film on a semiconductor substrate; (b) implanting n-type impurities into the silicon film in an nMOS region of the semiconductor substrate; (c) forming a conductive film on the silicon film; and (d) patterning the silicon film and the conductive film into a gate electrode.

Abstract: A semiconductor integrated circuit device and a method of manufacturing the same. The surface of a substrate of an active region surrounded by an element isolation trench is horizontally flat in the center portion of the active region but falls toward the side wall of the element isolation trench in the shoulder portion of the active region. This inclined surface contains two inclined surfaces having different inclination angles. The first inclined surface near the center portion of the active region is relatively steep and the second inclined surface near the side wall of the element isolation trench is gentler than the first inclined surface. The surface of the substrate in the shoulder portion of the active region is wholly rounded and has no angular portion.

Abstract: The present invention provides a method of forming first and second transistor devices. A first region of silicide is formed over a first portion of a gate dielectric that overlies a first well region in a semiconductor substrate. A second region of silicide is formed over a second portion of the gate dielectric. The second portion of the gate dielectric overlies a second well region in the semiconductor substrate. First and second doped junction regions are formed in the first and second well regions respectively.

Abstract: Embodiments include a semiconductor device including a well structure such that well areas can be formed with a higher density of integration and a plurality of high-voltage endurable transistors can be driven independently of one another with different voltages, and a method of manufacturing the semiconductor device. The semiconductor device may include a triple well comprising a first well formed in a silicon substrate and having a first conductivity type (P-type), a second well formed in adjacent relation to the first well and having a second conductivity type (N-type), and a third well formed in the second well and having the first conductivity type (P-type). A high-voltage endurable MOSFET is provided in each of the wells. Each MOSFET has an offset area in the corresponding well around a gate insulating layer. The offset area is formed of a low-density impurity layer which is provided under an offset LOCOS layer on the silicon substrate.

Abstract: MOS transistors and CMOS devices comprising a plurality of transistors including metal-based gate electrodes of different composition are formed by a process comprising: depositing a first blanket layer of a first metal on a thin gate insulator layer extending over first and second active device (e.g.

Abstract: A buried channel PMOS transistor for analog applications is integrated into a digital CMOS process. A third well region (105) is formed by implanting a region in the semiconductor substrate with all the n-type and p-type implants used to form the n-well and p-well regions for the digital CMOS process. A gate dielectric layer (50) and gate layer (109) are formed above the third well (105) and comprise the gate stack of the buried channel PMOS transistor. The implants used to form the drain extension regions and the source and drain regions of the CMOS transistors are used to complete the buried channel PMOS transistor.

Abstract: A first mask which is formed which exposes a cell array region and a peripheral circuit region of a semiconductor substrate. The cell array region and the peripheral circuit region are of a same conductive MOS type. Then, a preceding ion implantation process is implemented in both the cell array region and the peripheral circuit region utilizing the first mask. The preceding ion implantation process has ion implantation parameters corresponding to first implantation design specifications of one of the cell array region and the peripheral circuit region. Then, a second mask is formed which shields the one of the cell array region and the peripheral circuit region and which exposes the other of the cell array region and the peripheral circuit region. A subsequent ion implantation process is then implemented in the other of the cell array region and the peripheral circuit region utilizing the second mask.

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 new cascaded NMOS transistor output circuit with enhanced ESD protection is achieved. A driver PMOS transistor has the source connected to a voltage supply, the gate connected to the input signal, and the drain connected to the output pad. A dummy PMOS transistor has the source and the gate connected to the voltage supply, and the drain connected to the output pad. A driver NMOS cascaded stack comprises first and second NMOS transistors. The first NMOS transistor has the source connected to ground and the gate connected to the input signal. The second NMOS transistor has the gate connected to the voltage supply, the source connected to the first NMOS transistor drain, and the drain connected to the output pad. A p− implanted region underlies the n+ region of the drain but does not underlie the n+ region of the source. A dummy NMOS cascaded stack comprises third and fourth NMOS transistors. The third NMOS transistor has the gate and the source connected to ground.

Abstract: A semiconductor device having a shallow trench isolation (STI) structure, which is capable of reducing leakage current in a P-FET and improving the device characteristics of a memory device, and a manufacturing method thereof, including a semiconductor substrate having a first area with a first trench formed therein and a second area with a second trench formed therein; a first sidewall oxide layer formed on the inner surface of the first trench; a second sidewall oxide layer, which is thinner than the first sidewall oxide layer, formed on the inner surface of the second trench; a liner formed on the surfaces of the first and second sidewall oxide layers; and a dielectric material that fills the first and second trenches.

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 method of fabricating an HV-I/O ESD MOS device comprising the following steps. A structure having a first device region, a second device region and an HV-I/O ESD MOS device region is provided. A gate is formed over an oxide layer within the first device region. A gate is formed over an oxide layer within the second device region. A gate is formed over an oxide layer within the HV-I/O ESD MOS device region. The first device gate oxide layer is thinner than the second device gate oxide layer and the HV-I/O ESD MOS device gate oxide layer. The gate and oxide layers within each region have exposed side walls. An LV-LDD mask is formed over the gate and the structure within the second device region. An LV-LDD implant is performed into the structure adjacent the first device gate and the HV-I/O ESD MOS device gate to form first device LV-LDD implants and HV-I/O ESD MOS device LV-LDD implants. The LV-LDD mask is removed. An HV-LDD mask is formed over the gate and the structure within the first device region.

Abstract: A method (see e.g., FIG. 4) of fabricating a semiconductor device includes forming a trench 12 in a semiconductor body 10. A dielectric layer 26 is formed within the trench 12. Dielectric layer 26 lines the sidewall and, possibly, the bottom portions of the trench 12 in a manner where the thickness of the dielectric 26s at the sidewall is greater than the thickness of the dielectric 26b at the bottom. A dopant 28 can then be implanted into the semiconductor body beneath the trench.

Abstract: A method of fabricating a semiconductor device applies a LOCOS profile characteristic to an edge portion of an STI in a HV region to thereby lower compressive stress that is concentrated on the side of the STI. A field oxide film is formed so that only edge portions of HV region (active region II) may be in contact with a comparatively stiff STI, and then, a thick gate oxide film is formed on the HV region by utilizing a nitride film as a mask. After the nitride film as a mask is removed, a thin gate oxide film is formed on a LV region (an active region I in which a thin gate oxide film is formed). As a result, a thinning phenomenon of a gate oxide film at an edge portion of STI is prevented that otherwise would occur when the gate oxide film for HV grows in a normal STI structure by utilizing a nitride film as a mask.

Abstract: In a semiconductor device, a plurality of MIS transistors of the same conductivity type having different thresholds are formed at a main surface of semiconductor substrate, and impurity profiles on section extending in a depth direction from the main surface of the semiconductor substrate through respective channel regions of the plurality of MIS transistors have peaks located at different depths. This structure is formed by ion implantation performed on the respective channel regions with different implanting energies or different ion species. According to this semiconductor device, the thresholds of the MIS transistors can be individually controlled, and transistor characteristics optimum for uses can be obtained.

Abstract: An efficient method for fabricating dual well type structures uses the same number of masks used in single well type structure fabrication. In a preferred embodiment, the current invention allows low voltage and high voltage n-channel transistors and low voltage and high voltage p-channel transistors to be formed in a single substrate. One mask is used for forming a diffusion well, a second mask for both forming a retrograde well and doping the well to achieve an intermediate threshold voltage in that well, and a third mask for both differentiating the gate oxides for the low voltage devices and doping the threshold voltages to achieve the final threshold voltages.

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: 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: The present invention provides a CMOS process, wherein a halo structure can be fabricated without employing an additional lithographic mask for protecting the transistors of the opposite conductivity during a halo implant. The halo implant has a projected range or depth that lies in the range of an LIP implant or a counter-doping implant in the well containing the transistors of the opposite conductivity. The LIP or counter-doping implant effectively cancels the halo impurities.

Abstract: There is provided a method of fabricating a semiconductor device, including the steps of (a) forming both a p-well region and an n-well region at a surface of a semiconductor substrate, and (b) forming an n-type epitaxial layer on both the p- and n-well regions so that the n-type epitaxial layer contains impurities therein at a concentration lower than a concentration of impurities contained in the n-well region. For instance, the n-type epitaxial layer is formed by chemical vapor deposition in which a process gas including phosphorus or arsenic compounds therein is used. In accordance with the method, it is possible to optimize threshold voltages of both n-type and p-type transistors in a low-impurity channel transistor at a smaller number of steps. This ensures reduction in fabrication cost and enhancement in a fabrication yield.

Abstract: The present invention relates to formation of trench isolation structures that isolate active areas and a preferred doping in the fabrication of a CMOS device with a minimized number of masks. P-type dopant are implanted into a semiconductor substrate having therein a P-well and an N-well. Each of the N-well and P-well has therein a trench. The P-type dopant are implanted beneath each of the trenches in the P-well and the N-well to create a first P-type dopant concentration profile in the semiconductor substrate, wherein the P and N wells are substantially unimplanted by the P-type dopant in active areas adjacent to the respective trenches therein. A second implanting P-type dopant is made into the semiconductor substrate. The second implanting is beneath each of the trenches in the P and N wells to form a second P-type dopant concentration profile.

Abstract: Dynamic Random Access Memory (DRAM) cells are formed in a P well formed in a biased deep N well (DNW). PMOS transistors are formed in N wells. The NMOS channels stop implant mask is modified not to be a reverse of the N well mask in order-to block the channels stop implant from an N+ contact region used for DNW biasing. In DRAMS and other integrated circuits, a minimal spacing requirement between a well of an integrated circuit on the one hand and adjacent circuitry on the other hand is eliminated by laying out the adjacent circuitry so that the well is located adjacent to a transistor having an electrode connected to the same voltage as the voltage that biases the well. For example, in DRAMs, the minimal spacing requirement between the DNW and the read/write circuitry is eliminated by locating the DNW next to a transistor precharging the bit lines before memory accesses. One electrode of the transistor is connected to a precharge voltage.