Abstract: According to a semiconductor device of an embodiment of the present invention, a P-type buried diffusion layer is formed across a substrate and an epitaxial layer. An N-type buried diffusion layer is formed in the P-type buried diffusion layer. An overvoltage protective PN junction region is formed below an element formation region. A breakdown voltage of the PN junction region is lower than a source-drain breakdown voltage. This structure prevents a breakdown current from concentratedly flowing into the PN junction region and protects the semiconductor device from overvoltage.

Abstract: In a semiconductor device of the present invention, an N type epitaxial layer is divided into a plurality of element formation regions by an isolation region. In one of the element formation regions, a MOS transistor is formed. Around the MOS transistor, a protection element having a PN junction region is formed. The PN junction region has a junction breakdown voltage lower than that of a PN junction region of the MOS transistor. By use of this structure, when negative ESD surge is applied to a pad for a source electrode, the PN junction region of the protection element breaks down. Accordingly, the MOS transistor can be protected.

Abstract: In a semiconductor device of the present invention, an N type epitaxial layer is divided into a plurality of element formation regions by an isolation region. In one of the element formation regions, an NPN transistor is formed. Around the NPN transistor, a protection element having a PN junction region is formed. The PN junction region has a junction breakdown voltage lower than that of a PN junction region of the NPN transistor. By use of this structure, when negative ESD surge is applied to a pad for a base electrode, the PN junction region of the protection element breaks down. Accordingly, the NPN transistor can be protected.

Abstract: In a semiconductor device of the present invention, an N-type buried diffusion layer is formed across a substrate and an epitaxial layer. A P-type buried diffusion layer is formed across an upper surface of the N-type buried diffusion layer over a wide range to form a PN junction region for an overvoltage protection. A P-type diffusion region is formed so as to be connected to the P-type buried diffusion layer. A breakdown voltage of the PN junction region is lower than a breakdown voltage between a source and a drain. This structure makes it possible to prevent a concentration of a breakdown current and protect the semiconductor device from an overvoltage.

Abstract: In a semiconductor device of the present invention, an N-type epitaxial layer 2 is deposited on a P-type substrate 1. In the epitaxial layer 2, a P-type diffusion layer 5 to be used as a back gate region is formed. An N-type diffusion layer 8 to be used as a drain region is formed so as to surround the P-type diffusion layer 5. The P-type diffusion layer 5 and the N-type diffusion layer 8 partially overlap with each other. By use of a structure described above, a distance between a drain and a source is shortened. Thus, an ON resistance value can be reduced. Moreover, since a concentration gradient can be generated in the drain region, withstand pressure characteristics can be maintained while reducing an element formation region.

Abstract: In a zapping circuit of the present invention, resistances each formed of a polysilicon film or a tungsten silicon film are used as zapping elements. As driver elements for partially or completely fusing the resistances, low breakdown voltage MOS transistors are used. Using the MOS transistors makes it possible to reduce a region in which to form the driver elements for zapping, and to thus reduce an IC chip area.

Abstract: A semiconductor device includes a trench formed in a surface of a semiconductor substrate. A conductor is embedded in the trench. A conductive layer is arranged adjacent to the trench on the surface of the semiconductor substrate. Semiconductor elements, which include sources provided by one of the conductor and the conductive layer and drains provided by the other one of the conductor and the conductive layer, are formed in a semiconductor element formation region. A planar wiring layer is embedded in the semiconductor substrate under the entire semiconductor element formation region and connected to the conductor.

Abstract: In a semiconductor device of the present invention, an N type epitaxial layer is stacked on a P type single crystal silicon substrate. In the epitaxial layer, an N type diffusion layer as a base draw-out region, P type diffusion layers as an emitter region, and P type diffusion layers as a collector region are formed. The emitter region has a region having a larger diffusion width in a portion deeper than in a vicinity of a surface thereof. In a lateral PNP transistor, a smallest base width is formed in a deep portion of the epitaxial layer. By use of this structure, even in a case where the collector region is narrowed, a desired hfe value can be realized. Thus, the device size can be reduced.

Abstract: In a semiconductor device of the present invention, an N type epitaxial layer is stacked on a P type single crystal silicon substrate. In the epitaxial layer, an N type diffusion layer as a base draw-out region, P type diffusion layers as an emitter region, and P type diffusion layers as a collector region are formed. The emitter region has a region having a larger diffusion width in a portion deeper than in a vicinity of a surface thereof. In a lateral PNP transistor, a smallest base width is formed in a deep portion of the epitaxial layer. By use of this structure, recombination of free carriers (positive holes) on the surface is prevented. Thus, a desired hfe value can be realized.

Abstract: In a conventional semiconductor device, there is a problem that zener diode characteristics vary due to a crystal defect on a silicon surface, and the like. In a semiconductor device of the present invention, an N type epitaxial layer 4 is formed on a P type single crystal silicon substrate 2. In the epitaxial layer 4, P type diffusion layers 5, 6, 7 and 8 as anode regions and an N type diffusion layer 9 as a cathode region are formed. A PN junction region between the P type diffusion layer 8 and the N type diffusion layer 9 forms a zener diode 1. By use of this structure, a current path is located in a deep portion of the epitaxial layer 4. Thus, it is made possible to prevent a variation in a saturation voltage of the zener diode 1 due to a crystal defect on a surface of the epitaxial layer 4, and the like.

Abstract: In a semiconductor device of the present invention, an N type epitaxial layer is formed on a P type single crystal silicon substrate. The substrate and the epitaxial layer are partitioned into a plurality of element formation regions by isolation regions. Each of the isolation regions is formed of a P type buried diffusion layer and a P type diffusion layer coupled thereto. The P type buried diffusion layer is joined to N type buried diffusion layers on both sides thereof to form PN junction regions. On the other hand, the P type diffusion layer is joined to N type diffusion layers on both sides thereof to form PN junction regions. This structure suppresses extension of widthwise diffusion of the P type buried diffusion layer and the P type diffusion layer, thus making it possible to reduce the device size.

Abstract: According to a semiconductor device of an embodiment of the present invention, a P-type buried diffusion layer is formed across a substrate and an epitaxial layer. An N-type buried diffusion layer is formed in the P-type buried diffusion layer. An overvoltage protective PN junction region is formed below an element formation region. A breakdown voltage of the PN junction region is lower than a source-drain breakdown voltage. This structure prevents a breakdown current from concentratedly flowing into the PN junction region and protects the semiconductor device from overvoltage.

Abstract: In a conventional semiconductor device, for example, a MOS transistor, there is a problem that a parasitic transistor is prone to be operated due to an impurity concentration in a back gate region and a shape of diffusion thereof. In a semiconductor device of the present invention, for example, a MOS transistor, a P type diffusion layer 5 as the back gate region, and an N type diffusion layer 8 as a drain region, are formed in an N type epitaxial layer 4. In the P type diffusion layer 5, an N type diffusion layer 7 as a source region and a P type diffusion layer 6 are formed. The P type diffusion layer 6 is formed by performing ion implantation twice so as to correspond to a shape of a contact hole 15. Moreover, impurity concentrations in surface and deep portions of the P type diffusion layer 6 are controlled. By use of this structure, a device size is reduced, and an operation of a parasitic NPN transistor is suppressed.

Abstract: Disclosed is that in a method of manufacturing a semiconductor device of the present invention, when first and second P type diffusion layers using as a backgate region, these layers are formed in such a way that their impurity concentration peaks are shifted, respectively. Then, in the backgate region, a concentration profile of a region where an N type diffusion layer is formed is gradually established. After that, impurity ions, which form the N type diffusion layer, are implanted, and thereafter a thermal treatment is performed to diffuse the N type diffusion layer in a y shape at a lower portion of a gate electrode. This manufacturing method makes it possible to implement an electric filed relaxation in a drain region.

Abstract: In a semiconductor device of the present invention, a thin gate oxide film is formed on a P-type diffusion layer. On the gate oxide film, a gate electrode is formed. N-type diffusion layers are formed in the P-type diffusion layer, and the N-type diffusion layer is used as a drain region. The N-type diffusion layer is diffused in a ? shape at least below the gate electrode. With the structure described above, a diffusion region of the N-type diffusion layer expands and comes to be a low-concentration region in the vicinity of a surface of an epitaxial layer. Thus, it is possible to reduce an electric field from the gate electrode and an electric field between a source and a drain.

Abstract: In a semiconductor device of the present invention, an N-type epitaxial layer 2 is deposited on a P-type substrate 1. In the epitaxial layer 2, a P-type diffusion layer 5 to be used as a back gate region is formed. An N-type diffusion layer 8 to be used as a drain region is formed so as to surround the P-type diffusion layer 5. The P-type diffusion layer 5 and the N-type diffusion layer 8 partially overlap with each other. By use of a structure described above, a distance between a drain and a source is shortened. Thus, an ON resistance value can be reduced. Moreover, since a concentration gradient can be generated in the drain region, withstand pressure characteristics can be maintained while reducing an element formation region.

Abstract: In a conventional semiconductor device, there is a problem that an N-type diffusion region provided for protecting an element from an overvoltage is narrow and a breakdown current is concentrated so that a PN junction region for protection is broken. In a semiconductor device of the present invention, an N-type buried diffusion layer is formed across a substrate and an epitaxial layer. A P-type buried diffusion layer is formed across a wider region on an upper surface of the N-type buried diffusion layer so that a PN junction region for overvoltage protection is formed. A P-type diffusion layer is formed so as to be connected to the P-type diffusion layer. A breakdown voltage of the PN junction region is lower than a breakdown voltage between a source and a drain. With this structure, the concentration of the breakdown current is prevented so that the semiconductor device can be protected from the overvoltage.

Abstract: In a semiconductor device of the present invention, an N-type buried diffusion layer is formed across a substrate and an epitaxial layer. A P-type buried diffusion layer is formed across an upper surface of the N-type buried diffusion layer over a wide range to form a PN junction region for an overvoltage protection. A P-type diffusion region is formed so as to be connected to the P-type buried diffusion layer. A breakdown voltage of the PN junction region is lower than a breakdown voltage between a source and a drain. This structure makes it possible to prevent a concentration of a breakdown current and protect the semiconductor device from an overvoltage.

Abstract: In a manufacturing method of a semiconductor device according to the invention, a silicon oxide film, a polysilicon film, and silicon nitride film are deposited. An opening for forming a LOCOS oxide film is provided in the polysilicon film and the silicon nitride film. Then, using the opening, a P-type diffusion layer is formed by implanting ions by a self-alignment technique. Afterward, the LOCOS oxide film is formed on the opening. According to this manufacturing method, it becomes possible to form, with high alignment accuracy, the P-type diffusion layer used as a drain region in an off-set region.