Abstract: An integrated circuit having an n-channel MOSFET device and a JFET device. The integrated circuit includes a semiconductor layer having an upper surface, an MOS transistor device formed in a doped well of a first conductivity type extending from the semiconductor upper surface and a JFET device. The JFET device includes a channel region in the semiconductor layer spaced from, and having a peak concentration positioned a predetermined distance below, the upper surface. An associated method of manufacturing includes introducing p-type dopant into the semiconductor surface to form a p-well in which the NMOS device is formed and a source and a drain of the JFET device. N-type dopant is introduced into the semiconductor surface to form an n-type region of the NMOS device below the p-well and a gate region of the JFET device.

Abstract: Example embodiments are directed to a junction field effect thin film transistor (JFETFT) including a first electrode formed on a substrate, a first conductive first gate semiconductor pattern formed on the first gate electrode, a second conductive semiconductor channel layer formed on the substrate and the first conductive first gate semiconductor pattern, and source and drain electrodes formed on the second conductive semiconductor pattern and located at both sides of the first conductive gate semiconductor pattern. The JFETFT may further include a first conductive second gate semiconductor pattern formed on a portion of the second conductive semiconductor channel layer between the source electrode and the drain electrode, and a second gate electrode formed on the first conductive second gate semiconductor pattern.

Abstract: A semiconductor device includes a substrate of semiconductor material. A source region, a drain region, and a conducting region of the semiconductor device are formed in the substrate and doped with a first type of impurities. The conducting region is operable to conduct current between the drain region and the source region when the semiconductor device is operating in an on state. A gate region is also formed in the substrate and doped with a second type of impurities. The gate region abuts a channel region of the conducting region. A stress layer is deposited on at least a portion of the conducting region. The stress layer applies a stress to the conducting region along a boundary of the conducting region that strains at least a portion of the conducting region.

Abstract: An integrated circuit having fully-depleted silicon-on-insulator (FD-SOI) transistors and bulk transistors on a semiconductor substrate is disclosed.

Abstract: An integrated Junction Field Effect Transistor is disclosed which is much smaller and much less expensive to fabricate because it does not use Shallow Trench Isolation or field oxide in the semiconductor substrate to isolate separate transistors. Instead, a layer of insulating material is formed on the top surface of said substrate, and interconnect trenches are etched in said insulating layer which do not go all the way down to the semiconductor substrate. Contact openings are etched in the insulating layer all the way down to the semiconductor layer. Doped poly-silicon is formed in the contact openings and interconnect trenches and silicide is formed on tops of the poly-silicon. This contact and interconnect structure applies to any integrated transistor. The integrated JFET disclosed herein does not use STI or field oxide and uses junction isolation. A conventional JFET is built in a P-well. The P-well is encapsulated in an N-well which is implanted into the substrate.

Abstract: A non-volatile semiconductor memory device, which is intended to prevent data destruction by movements of electric charges between floating gates and thereby improve the reliability, includes element isolation/insulation films buried into a silicon substrate to isolate stripe-shaped element-forming regions. Formed on the substrate are a floating gate via a first gate insulating film and further a control gate via a second gate insulating film. Source and drain diffusion layers are formed in self-alignment with control gates. The second gate insulating film on the floating gate is divided and separated together with the floating gate by slits above the element isolation/insulation films into discrete portions of individual memory cells.

Abstract: A semiconductor device can include at least a first diffusion region formed by doping a semiconductor substrate and at least a second diffusion region formed by doping the semiconductor substrate that is separated from the first diffusion region by an isolation region. At least a first conductive line can comprise a semiconductor material formed over and in contact with the first diffusion region and the second diffusion region. A portion of the first conductive line in contact with the first diffusion region is doped to an opposite conductivity type as the first diffusion region. At least a second conductive line comprising a semiconductor material is formed in parallel with the first conductive line and over and in contact with the first diffusion region and the second diffusion region. A portion of the second conductive line can be in contact with the first diffusion region and doped to a same conductivity type as the first diffusion region.

Abstract: An insulating film is provided in a region surrounding a circuit region on a p type silicon substrate, and a frame-shaped electrode is provided to surround the circuit region on the insulating film. The region directly under the electrode at the surface of the p type silicon substrate is formed as a non-doped region with no impurity implanted. Then, a positive power supply potential is applied to the electrode. In this way, a depletion layer is formed directly under the electrode at the surface of the p type silicon substrate. Consequently, the substrate noise is shielded.

Abstract: To provide a semiconductor device that permits free setting of characteristics of individual semiconductor elements which are mixedly mounted and have different characteristics, and is free of steps between formed semiconductor elements, in a manufacturing method for the semiconductor device, an n-type silicon layer is deposited on a p-type silicon substrate by epitaxial growth, and then an SOI layer is deposited thereon through the intermediary of a BOX layer. A junction transistor using a part of the n-type silicon layer as a channel region and a MOS transistor using the SOI layer are produced.

Abstract: In accordance with an embodiment of the present invention, a MOSFET includes at least two insulation-filled trench regions laterally spaced in a first semiconductor region to form a drift region therebetween, and at least one resistive element located along an outer periphery of each of the two insulation-filled trench regions. A ratio of a width of each of the insulation-filled trench regions to a width of the drift region is adjusted so that an output capacitance of the MOSFET is minimized.

Abstract: A semiconductor device is provided, which comprises a semiconductor layer over an insulating surface, and an insulating layer over the semiconductor layer. The semiconductor layer includes at least two element regions, and an element separation region. The element separation region is disposed between the two element regions. The element separation region includes at least one impurity element selected from the group consisting of oxygen, nitrogen, and carbon. The element separation region has higher resistance than a first source and drain regions included in one of the two element regions and a second source and drain regions included in the other of the two element regions.

Abstract: Junction field effect transistors (JFETs) can be fabricated with an epitaxial layer that forms a sufficiently thick channel region to enable the JFET for use in high voltage applications (e.g., having a breakdown voltage greater than about 20V). Additionally or alternatively, threshold voltage (VT) implants can be introduced at one or more of the gate, source and drain regions to improve noise performance of the JFET. Additionally, fabrication of such a JFET can be facilitated forming the entire JFET structure concurrently with a CMOS fabrication process and/or with a BiCMOS fabrication process.

Abstract: Silicon carbide metal-oxide semiconductor field effect transistors (MOSFETs) may include an n-type silicon carbide drift layer, a first p-type silicon carbide region adjacent the drift layer and having a first n-type silicon carbide region therein, an oxide layer on the drift layer, and an n-type silicon carbide limiting region disposed between the drift layer and a portion of the first p-type region. The limiting region may have a carrier concentration that is greater than the carrier concentration of the drift layer. Methods of fabricating silicon carbide MOSFET devices are also provided.

Abstract: A semiconductor structure includes an isolation ring disposed on a semiconductor substrate, surrounding first and second circuit areas. A buried isolation layer is continuously extended through the first circuit area and the second circuit area, in the semiconductor substrate. The buried isolation layer interfaces with the isolation ring, thereby isolating the first and second circuit areas from a backside bias of the semiconductor substrate. An ion enhanced isolation layer separates the first well in the first circuit area and the second well in the second circuit areas from the isolation ring and the buried isolation layer, thereby preventing punch-through between the wells of the circuit areas and the buried isolation layer.

Abstract: A technique enabling to improve element isolation characteristic of a semiconductor device is provided. An element isolation structure is provided in a semiconductor substrate in which a silicon layer, a compound semiconductor layer and a semiconductor layer are laminated in this order. The element isolation structure is composed of a trench, a semiconductor film, and first and second insulating films. The trench extends through the semiconductor layer and extends to the inside of the compound semiconductor layer. The semiconductor film is provided on the surface of the trench, and the first insulating film is provided on the semiconductor film. The second insulting film is provided on the first insulating film and fills the trench.

Abstract: A floating-gate transistor for an integrated circuit is formed on a p-type substrate. An n-type region is disposed over the p-type substrate. A p-type region is disposed over the n-type region. Spaced apart n-type source and drain regions are disposed in the p-type region forming a channel therein. A floating gate is disposed above and insulated from the channel. A control gate is disposed above and insulated from the floating gate. An isolation trench disposed in the p-type region and surrounding the source and drain regions, the isolation trench extending down into the n-type region. The substrate, the n-type region and the p-type region each biased such that the p-type region is fully depleted.

Abstract: A high resistance region may be used to isolate the body of a first transistor from a body contact.

Abstract: A first insulation film, a first conductor film, and a cap are sequentially formed on a semiconductor substrate. The first insulation film, the first conductor film, and the cap, and the substrate are etched in the same pattern. A second insulation film is placed in that etched pattern. The cap is removed. A second conductor film is formed on the side face of the second insulation film.

Abstract: A method for fabricating a dual gate structure for JFETs and MESFETs and the associated devices. Trenches are etched in a semiconductor substrate for fabrication of a gate structure for a JFET or MESFET. A sidewall spacer may be formed on the walls of the trenches to adjust the lateral dimension for a first gate. Following the formation of the first gate by implantation or deposition, a buffer region is implanted below the first gate using a complementary dopant and a second sidewall spacer with a thickness that may be the same or greater than the thickness of the first sidewall spacer. Subsequent to the buffer implant, a second gate is implanted beneath the buffer layer using a third sidewall spacer with a greater thickness than the first sidewall spacer.

Abstract: A power device includes a gate electrode, a source electrode, and a drain electrode provided within an active region of a semiconductor substrate of first conductivity type. A vertical diffusion region of second conductivity is provided at a periphery the active region. The vertical diffusion region extends continuously from a top surface of the substrate to a bottom surface of the substrate. The vertical diffusion region includes an upper portion having a first depth and a lower portion having a second depth that is substantially greater than the first depth.

Abstract: Active areas of a Dynamic Random Access Memory (DRAM) formed on a semiconductor substrate are defined by buried bit lines on two sides and by conductors separated from the semiconductor substrate by electrically insulating layers on two other sides. The conductors are electrically biased during operation of the DRAM to cause portions of the semiconductor substrate therebelow to increase in majority carrier concentration and thus to inhibit inversion thereof. Each buried bit line is formed in a trench in the semiconductor substrate. Each trench houses a separate bit line and is lined with an electrical insulator and has a conductor in a bottom portion thereof.

Abstract: A silicon-on-insulator (SOI) gated diode and non-gated junction diode are provided. The SOI gated diode has a PN junction at the middle region under the gate, and which has more junction area than a normal diode. The SOI non-gated junction diode has a PN junction at the middle region thereof, and then also has more junction area than a normal diode. The SOI diodes of the present invention improve the protection level offered for electrical overstress (EOS)/electrostatic discharge (ESD) due to the low power density and heating for providing more junction area than normal ones. The I/O ESD protection circuits, which comprise primary diodes, a first plurality of diodes, and a second plurality of diodes, all of which are formed of the present SOI diodes, could effectively discharge the current when there is an ESD event. And, the ESD protection circuits, which comprise more primary diodes, could effectively reduce the parasitic input capacitance, so that they can be used in the RF circuits or HF circuits.

Abstract: A dummy active region is formed in which abrading processes are averaged. A semiconductor device is characterized in that an active region for forming an actual device, a device separation region being formed by a trench, and a dummy active region formed substantially in a rectangular shape are included, and the length of the short side of the dummy active region is less than 1 ?m.

Abstract: A capacitor for a semiconductor device and a method of manufacturing a capacitor for a semiconductor device is disclosed that uses radial current flow. The capacitor includes a semiconductor substrate that includes a plurality of insulation islands. An insulation layer is formed over the semiconductor substrate. Gate electrodes are formed on top of the insulation layer. An array of CD contact pads including a plurality of CD contacts are connected to the semiconductor substrate in a first predetermined number of locations. An array of CG contact pads including at least one CG contact connected to the gate electrodes such that each CG contact is connected to a respective gate electrode above a respective insulation island in a second predetermined number of locations.

Abstract: In an embodiment of an integrated circuit structure having buried layer substrate isolation and a method for forming same, a buried layer having conductivity type opposite to that of an overlying well region is used for wells containing transistors prone to noise generation, where the wells are of the same conductivity type as the substrate. The buried layer may in some embodiments include a first portion underlying the transistor and a second portion spaced apart from and laterally surrounding the first portion. In some embodiments, the circuit may include a doped annular region of the same conductivity type as the buried layer, where the annular region contacts a portion of the buried layer and laterally surrounds the transistor. The circuit may further include metallization adapted to connect the well and annular region to opposite polarities of a power supply voltage, or in some embodiments to preclude such connection.

Abstract: A method for fabricating a junction field effect transistor (JFET) with a double dose gate structure. A trench is etched in the surface of a semiconductor substrate, followed by a low dose implant to form a first gate region. An anneal may or may not be performed after the low dose implant. A gate definition spacer is then formed on the wall the trench to establish the lateral extent of a second, high dose implant gate region. After the second implant, the gate is annealed. The double dose gate structure produced by the superposition of two different and overlapping regions provides an additional degree of flexibility in determining the ultimate gate region doping profile. A further step comprises using the gate definition spacer to define the walls of a second etched trench that is used to remove a portion of the p-n junction, thereby further reducing the junction capacitance.

Abstract: A CMOS or NMOS device has one or more n-channel FETs disposed on a substrate, the device being resistant to total dose radiation failures, the device further including a negative voltage source, for applying a steady negative back bias to the substrate of the n-channel FETs to mitigate leakage currents in the device, thereby mitigating total dose radiation effects. A method for operating a CMOS or NMOS device to resist total dose radiation failures, the device having one or more n-channel FETs disposed on a substrate, has the steps: (a) disposing the CMOS or NMOS device in a radiation environment, the radiation environment delivering a dose on the order of tens or hundreds of krad (Si) over the period of use of the CMOS device; and (b) applying a negative back bias to the substrate of the NMOS FETs, at a voltage for mitigating leakage currents about the n-channel FETs.

Abstract: Techniques to isolate noise-sensitive circuits from noise generated by nearby circuits. In one design, a quiet region is formed on a die when surrounded by a deep n-well formed on top of a p-type substrate. The deep n-well is heavily doped n-type and forms a depletion region at the junction with the p-type substrate. The depth and width of the depletion region is dependent on the doping concentration of the deep n-well and the amount of reverse bias voltage applied to the deep n-well. In general, a wider and deeper depletion region may be formed by more heavily doping the deep n-well and applying a higher reverse bias voltage. By properly constructing the deep n-well and applying a high reverse bias voltage, a deep and wide depletion region may be formed to provide a barrier against noise from entering the quiet region.

Abstract: A microelectronic structure with a low voltage part and high voltage part, such that the low voltage part is protected against the high voltage part and process of obtaining this protection. The structure includes at least one low-voltage element (2) and at least high-voltage element (4) formed on a semi-conductor substrate (6). According to the invention, at least one channel (18) is formed, passing through the low-voltage element and one semi-conductor zone is formed with doping opposite to that of the substrate, at least around the walls of the channel or channels and a contact point (24) is established in this zone. Application to smart power integrated circuits.

Abstract: Techniques to isolate noise-sensitive circuits from noise generated by nearby circuits. In one design, a quiet region is formed on a die when surrounded by a deep n-well formed on top of a p-type substrate. The deep n-well is heavily doped n-type and forms a depletion region at the junction with the p-type substrate. The depth and width of the depletion region is dependent on the doping concentration of the deep n-well and the amount of reverse bias voltage applied to the deep n-well. In general, a wider and deeper depletion region may be formed by more heavily doping the deep n-well and applying a higher reverse bias voltage. By properly constructing the deep n-well and applying a high reverse bias voltage, a deep and wide depletion region may be formed to provide a barrier against noise from entering the quiet region.

Abstract: A detector of the state (on or off) of a vertical power component formed in a lightly-doped semiconductor substrate of a first conductivity type having a front surface and a rear surface. The region corresponding to the power component is surrounded with an isolating wall of opposite type to that of the substrate. This state detector is formed outside of said region and is formed with a vertical detection component, the state of which is switched by parasitic charges propagating outside of the isolating wall when the power component is on.

Abstract: The present invention provides methods of manufacturing a field oxide isolation structure over a semiconductor. One of the methods includes the steps of: (1) depositing a first stack-nitride sublayer over the semiconductor at a first deposition rate and (2) subsequently depositing a second stack-nitride sublayer over the first stack-sublayer at a second deposition rate that is either greater or less than the first deposition rate. The first and second deposition rates provide first and second stack-nitride sublayers that cooperate to form a relatively thin, uniform thickness of the field oxide isolation structure over the semiconductor and provide a stress-accommodating system within the semiconductor. The varying rates of deposition and accompanying changes in mixture ratio, produce a stack that is better able to absorb stress, has greater uniformity and is far less subject to the disadvantageous phenomenon of stack-lifting, particularly encountered in semiconductor having a PADOX layer deposited thereon.

Abstract: A semiconductor device and a method of forming thereof include a dummy active region positioned adjacent the device active region. The dummy active region is formed to include an oxide layer of a thickness that is less than the oxide layer of the active region such that excess charge accumulated during etching in the active region is conducted through the dummy active region into the substrate. In this manner, the dummy active region operates as a charge sink during formation of the active region to prevent premature deterioration of the gate oxide layer of the active region.

Abstract: Conventionally, an insulating film for element isolation has had a uniformly large thickness either in a memory cell area and in a peripheral circuit area so that the total film thickness of the memory cell area having a floating gate electrode, a control gate electrode, and an erase gate electrode is extremely increased, resulting in a large height difference between the memory cell area and the peripheral circuit area. The insulating film for element isolation in the peripheral circuit area should be thick, while the insulating films for element isolation in the memory cell area need not be as thick as the insulating film for element isolation in the peripheral circuit area in terms of operation.

Abstract: The present invention relates to an isolating wall for separating elementary components formed in different wells, a component located in at least one of the wells being capable of operating with a high current density. The isolating wall exhibits in its median portion a concentration of carriers higher than 1016 atoms/cm3. Preferably, the width of the openings from which the dopant diffusions are formed in the upper and lower surfaces of the substrate is higher than 1.3 times the half-thickness of the substrate.

Abstract: A semiconductor device (10) uses a plurality of floating field conductors (26, 28) to provide a substantially uniform electric field along the surface of the drift region (17) of the device (10). This substantially uniform electric field increases the breakdown voltage per unit length of the drift region (17).

Abstract: An arrangement (100) has a low voltage circuit (196') on a first doped well (110) and a high voltage circuit (197') on a second doped well (120) integrated into a common semiconductor substrate (105). The first well (110) laterally extends along a surface (106) of the substrate (105) to provide a voltage drop (.vertline.V.sub.LARGE .vertline.) between a first end (111) and a second end (112) so that potential differences between the circuits (196', 197') are substantially isolated. The low voltage circuit (196') controls a current from the second end (112) to provide a variable potential (by .vertline.V.sub.SMALL .vertline.) at the second end (112) which is communicated to other parts (193') of the second circuit (197') by a connection (150). The wells (110, 120) are spaced to provide isolation for potential magnitude changes between the second end (112) of the first well (110) and the second well (120) which are invoked by the first circuit (196').

Abstract: A semiconductor device formed on an epitaxial substrate includes a high-resistance region in the vicinity of an interface between a doped semiconductor substrate and an epitaxial layer thereon. The high-resistance region is advantageously formed by an ion implantation process of a dopant opposite to a dopant contained in the doped semiconductor substrate such that there is formed a depletion of carriers in the vicinity of the foregoing interface.

Abstract: A dielectric isolated high voltage semiconductor device having an arrangement for extending a depletion layer of a main junction beyond an insulating layer containing an island to a semiconductor supporter by applying the same reverse biasing voltage to the supporter and the islands. That is, in the structure, an electrode is provided at the back surface of the supporter and connected to a main electrode of the selected island. The above-mentioned main junction is the pn junction to which the reverse biasing voltage for securing the withstand voltage of the semiconductor device is applied. The device is structured, also, with high impurity concentration regions for preventing a depletion layer, formed during a reverse biasing of the main junction of a circuit element of an island, from extending into adjacently disposed islands.

Abstract: A method of semiconductor fabrication includes the steps of forming a dielectric layer on a first surface of a semiconductor wafer having a plurality of laterally distributed semiconductor devices selectively interconnected on the first surface and bonding a support substrate to the first surface of the semiconductor wafer on the dielectric layer to form a composite structure. A portion of the semiconductor wafer from a second surface which is opposite the first surface is removed and the second surface of the semiconductor wafer is processed. Processing of the second surface optionally includes the formation of isolation trenches electrically isolating the laterally distributed semiconductor devices.

Abstract: A semiconductor integrated circuit has a semiconductor substrate on which macrocells are formed. At least one of the macrocells is surrounded by a first diffused region, which may be surrounded by a second diffused region. The first and second diffused regions are connected to power source terminals, respectively. Semiconductor elements included in each macrocell are connected to power source terminals that are independent of the terminals connected to the diffused regions. Alternatively, a voltage is supplied to the diffused regions through power lines that are different from power lines for the semiconductor elements. This arrangement absorbs short-circuit current in CMOS circuitry and/or substrate current produced by the semiconductor elements.

Abstract: A semiconductor device having the grounds of element regions are provided in a semiconductor substrate. The device comprises a semiconductor substrate of a first conductivity type, at least two element regions of a second conductivity type, provided in a semiconductor substrate and having grounds connected to said semiconductor substrate when said semiconductor substrate is set at a fixed potential and at least one ground-isolating well region of the second conductivity type, provided between said at least two element regions to electrically isolate said at least two element regions by forming a depletion layer between said at least two element regions when applied with a reverse bias voltage.

Abstract: A semiconductor arrangement with a vertical power semiconductor switch and an integrated CMOS or bipolar circuit is provided, whereby the integrated CMOS or bipolar circuit is arranged on a semiconductor islet insulated from a first semiconductor material region by a buried insulating layer. The first semiconductor material region is included as a part of the structure of the power semiconductor switch. The buried insulating layer is surrounded by a second semiconductor material region arranged between it and the first semiconductor material region, the doping of which is the opposite of that of the first semiconductor material region. The second semiconductor region is coupled to the first semiconductor region by a circuit. This circuit does not directly connect the potential of the second semiconductor material region with the potential of the first semiconductor material region.

Abstract: Pin electronics for an IC tester are built as an integrated circuit for characterizing the electrical operation of a device under test (DUT) by applying a test voltage to each of the pins on the DUT and measuring each resulting current. Typically, an IC tester selects one of several measure resistors, applies a stimulus to a pin of the DUT using an input driver, and measures the current response of the DUT through the related measure resistor. Each measure resistor corresponds to a specific current range and measurement accuracy is proportional to the precision of the selected resistor. Each measure resistor is a series of precision integrated resistors having a very low leakage current. This provides for current measurements of high sensitivity.

Abstract: A large sense voltage is produced by the semiconductor device of the present invention. The semiconductor device, utilizing current mirror techniques, is comprised of a power MOSFET having a plurality of power cells and a plurality of sense cells formed in a semiconductor epitaxial layer. The large sense voltage is provided by isolating and separating the plurality of power cells from the plurality of sense cells by at least the thickness of the semiconductor epitaxial layer. Isolation can be provided by forming a plurality of inactive cells or an elongated cell between the plurality of power cells and the plurality of sense cells. In addition, high voltage capabilities can be maintained by including a partially active region adjacent the power cells to provide for good termination.

Abstract: A semiconductor device is supported by a semiconductor body which comprises a substrate, an oxide layer and a weakly doped monocrystalline wafer. Trenches for a dielectrically isolating layer which surrounds a component region are etched in the wafer. A field effect transistor in the component region has two doped wafer-line gate regions, which have been diffused in the component region with the aid of a first mask. Two heavily doped regions are diffused in the component region with the aid of a second mask, these regions forming the source region and the drain region of the transistor. The semiconductor body is easy to produce and is available commercially, which simplifies manufacture of the field effect transistor. Manufacture is also simplified because the configuration of both the component region and the parts of the transistor are determined by the simple choice of masks. The component region is weakly doped and is easy to deplete of charge carriers.

Abstract: The structure and method of this invention provide, for example, electrical isolation between active elements in adjacent rows and/or columns of an integrated circuit by use of a self-aligned field-plate conductor formed over and insulated from the substrate regions that are bounded by the channel regions of field-effect transistors in adjacent rows and that are bounded by the bitlines forming those transistors in a column. The field-plate conductor is formed, for example, in a strip that extends over the isolation areas and thermal insulator regions between row lines of the memory cell array. The field-plate conductor strip is connected to a voltage supply that has a potential with respect to the potential of the semiconductor substrate which causes the isolation areas to be nonconductive. Component density may be increased over that of prior-art structures and methods.

Abstract: A semiconductor device includes an impurity doped polycrystalline silicon layer formed on a first conductivity type semiconductor substrate with an oxide film provided therebetween, an interlayer insulation layer formed on the polycrystalline silicon layer and provided with a contact hole using the surface of the silicon layer as a bottom surface, and a conductive wiring layer formed on the surface of the interlayer insulation layer and on the inner wall surface of said contact hole. A second conductivity type impurity diffusion layer is formed at a region of the surface of the semiconductor substrate located below the contact hole. A pn junction formed between the impurity diffusion layer and the semiconductor substrate ensures insulation against its reverse bias voltage to prevent leakage current to the semiconductor substrate.