Abstract: A silicon carbide substrate includes a first layer of a first conductivity type, a second layer of a second conductivity type provided on the first layer, and a third layer provided on the second layer and doped with an impurity for providing the first conductivity type. The silicon carbide substrate has a trench formed through the third layer and the second layer to reach the first layer. The first layer has a concentration peak of the impurity in a position away from the trench in the first layer. As a result, a silicon carbide semiconductor device having an electric field relaxation structure that can be readily formed is provided.

Abstract: A drift layer has a thickness direction throughout which a current flows and has an impurity concentration N1d for a first conductivity type. A body region is provided on a portion of the drift layer, has a channel to be switched by a gate electrode, has an impurity concentration N1b for the first conductivity type, and has an impurity concentration N2b for the second conductivity type greater than the impurity concentration N1b. A JFET region is disposed adjacent to the body region on the drift layer, has an impurity concentration N1j for the first conductivity type, and has an impurity concentration N2j for the second conductivity type smaller than the impurity concentration N1j. N1j?N2j>N1d and N2j<N2b are satisfied.

Abstract: A silicon carbide semiconductor device has a planar layout configured by periodically arranging unit cells. The unit cells include valid cells and invalid cells. Each of the valid cells has a switchable channel surface. The invalid cells are to relax electric field in the valid cells. At least one of the valid cells is disposed between adjacent ones of the invalid cells.

Abstract: An IGBT, which is capable of reducing on resistance by reducing channel mobility, includes: an n type substrate made of SiC and having a main surface with an off angle of not less than 50° and not more than 65° relative to a plane orientation of {0001}; a p type reverse breakdown voltage holding layer made of SiC and formed on the main surface of the substrate; an n type well region formed to include a second main surface of the reverse breakdown voltage holding layer; an emitter region formed in the well region to include the second main surface and including a p type impurity at a concentration higher than that of the reverse breakdown voltage holding layer; a gate oxide film formed on the reverse breakdown voltage holding layer; and a gate electrode formed on the gate oxide film. In a region including an interface between the well region and the gate oxide film, a high-concentration nitrogen region is formed to have a nitrogen concentration higher than those of the well region and the gate oxide film.

Abstract: A semiconductor device includes: a substrate made of silicon carbide and having a main surface having an off angle of not less than ?3° and not more than +5° relative to a (0-33-8) plane in a <01-10> direction; a p type layer made of silicon carbide and formed on the main surface of the substrate by means of epitaxial growth; and an oxide film formed in contact with a surface of the p type layer. A maximum value of nitrogen atom concentration is 1×1021 cm?3 or greater in a region within 10 nm from an interface between the p type layer and the oxide film.

Abstract: A MOSFET, which is capable of reducing on resistance by reducing channel mobility even when a gate voltage is high, includes: an n type substrate made of SiC and having a main surface with an off angle of 50°-65° relative to a {0001} plane; an n type reverse breakdown voltage holding layer made of SiC and formed on the main surface of the substrate; a p type well region formed in the reverse breakdown voltage holding layer distant away from a first main surface thereof; a gate oxide film formed on the well region; an n type contact region disposed between the well region and the gate oxide film; a channel region connecting the n type contact region and the reverse breakdown voltage holding layer; and a gate electrode disposed on the gate oxide film. In a region including an interface between the channel region and the gate oxide film, a high-concentration nitrogen region is formed.

Abstract: A MOSFET includes a semiconductor substrate having a trench formed in a main surface, a gate oxide film, a gate electrode, and a source interconnection. A semiconductor substrate includes an n-type drift layer and a p-type body layer. The trench is formed to penetrate the body layer and to reach the drift layer. The trench includes an outer peripheral trench arranged to surround an active region when viewed two-dimensionally. On the main surface opposite to the active region when viewed from the outer peripheral trench, a potential fixing region where the body layer is exposed is formed. The source interconnection is arranged to lie over the active region when viewed two-dimensionally. The potential fixing region is electrically connected to the source interconnection.

Abstract: A collector layer having p type is formed on a silicon carbide substrate having n type. A drift layer having n type is formed on a top surface side of the collector layer. A body region provided on the drift layer and having p type, and an emitter region provided on the body region to be separated from the drift layer by the body region and having n type are formed. A bottom surface side of the collector layer is exposed by removing the silicon carbide substrate.

Abstract: A first layer has n type conductivity. A second layer is epitaxially formed on the first layer and having p type conductivity. A third layer is on the second layer and having n type conductivity. ND is defined to represent a concentration of a donor type impurity. NA is defined to represent a concentration of an acceptor type impurity. D1 is defined to represent a location in the first layer away from an interface between the first layer and the second layer in a depth direction. D1 in which 1?ND/NA?50 is satisfied is within 1 ?m therefrom. A gate trench is provided to extend through the third layer and the second layer to reach the first layer. A gate insulating film covers a side wall of the gate trench. A gate electrode is embedded in the gate trench with the gate insulating film interposed therebetween.

Abstract: A substrate is provided with a main surface having an off angle of 5° or smaller relative to a reference plane. The reference plane is a {000-1} plane in the case of hexagonal system and is a {111} plane in the case of cubic system. A silicon carbide layer is epitaxially formed on the main surface of the substrate. The silicon carbide layer is provided with a trench having first and second side walls opposite to each other. Each of the first and second side walls includes a channel region. Further, each of the first and second side walls substantially includes one of a {0-33-8} plane and a {01-1-4} plane in the case of the hexagonal system and substantially includes a {100} plane in the case of the cubic system.

Abstract: A mask layer is formed on a silicon carbide layer by a deposition method. The mask layer is patterned. A gate trench having a side wall is formed by removing a portion of the silicon carbide layer by etching using the patterned mask layer as a mask. A gate insulating film is formed on the side wall of the gate trench. A gate electrode is formed on the gate insulating film. The silicon carbide layer has one of hexagonal and cubic crystal types, and the side wall of the gate trench substantially includes one of a{0-33-8} plane and a {01-1-4} plane in a case where the silicon carbide layer is of hexagonal crystal type, and substantially includes a {100} plane in a case where the silicon carbide layer is of cubic crystal type.

Abstract: A substrate has a surface made of a semiconductor having a hexagonal single-crystal structure of polytype 4H. The surface of the substrate is constructed by alternately providing a first plane having a plane orientation of (0-33-8), and a second plane connected to the first plane and having a plane orientation different from the plane orientation of the first plane. A gate insulating film is provided on the surface of the substrate. A gate electrode is provided on the gate insulating film.

Abstract: A MOSFET includes a silicon carbide substrate, a drift layer made of silicon carbide and including a main surface having an off angle of 50° or more and 65° or less with respect to a {0001} plane, and a gate oxide film formed on and in contact with the main surface of the drift layer. The drift layer includes a p type body region formed to include a region in contact with the gate oxide film. The p type body region has an impurity density of 5×1016 cm?3 or more. A plurality of p type regions of p conductivity type located apart from one another in a direction perpendicular to a thickness direction of the drift layer are arranged in a region in the drift layer lying between the p type body region and the silicon carbide substrate.

Abstract: A drift layer has a thickness direction throughout which a current flows and has an impurity concentration N1d for a first conductivity type. A body region is provided on a portion of the drift layer, has a channel to be switched by a gate electrode, has an impurity concentration N1b for the first conductivity type, and has an impurity concentration N2b for the second conductivity type greater than the impurity concentration N1b. A JFET region is disposed adjacent to the body region on the drift layer, has an impurity concentration N1j for the first conductivity type, and has an impurity concentration N2j for the second conductivity type smaller than the impurity concentration N1j. N1j?N2j>N1d and N2j<N2b are satisfied.

Abstract: A method of manufacturing a MOSFET includes the steps of preparing a silicon carbide substrate, forming an active layer on the silicon carbide substrate, forming a gate oxide film on the active layer, forming a gate electrode on the gate oxide film, forming a source contact electrode on the active layer, and forming a source interconnection on the source contact electrode. The step of forming the source interconnection includes the steps of forming a conductor film on the source contact electrode and processing the conductor film by etching the conductor film with reactive ion etching. Then, the method of manufacturing a MOSFET further includes the step of performing annealing of heating the silicon carbide substrate to a temperature not lower than 50° C. after the step of processing the conductor film.

Abstract: A silicon carbide semiconductor device having excellent electrical characteristics including channel mobility and a method for manufacturing the same are provided. The method for manufacturing a silicon carbide semiconductor device includes: an epitaxial layer forming step of preparing a semiconductor film of silicon carbide; a gate insulating film forming step of forming an oxide film on a surface of the semiconductor film; a nitrogen annealing step of performing heat treatment on the semiconductor film on which the oxide film is formed, in a nitrogen-containing atmosphere; and a post heat treatment step of performing, after the nitrogen annealing step, post heat treatment on the semiconductor film on which the oxide film is formed, in an atmosphere containing an inert gas. The heat treatment temperature in the post heat treatment step is higher than that in the nitrogen annealing step and lower than a melting point of the oxide film.

Abstract: An MOSFET includes a silicon carbide substrate, an active layer, a gate oxide film, and a gate electrode. The active layer includes a body region where an inversion layer is formed at a region in contact with the gate oxide film by application of voltage to the gate electrode. The body region includes a low concentration region arranged at a region where an inversion layer is formed, and containing impurities of low concentration, and a high concentration region adjacent to the low concentration region in the carrier mobile direction in the inversion layer, arranged in a region where the inversion layer is formed, and containing impurities higher in concentration than in the low concentration region.

Abstract: A silicon carbide layer is epitaxially formed on a main surface of a substrate. The silicon carbide layer is provided with a trench having a side wall inclined relative to the main surface. The side wall has an off angle of not less than 50° and not more than 65° relative to a {0001} plane. A gate insulating film is provided on the side wall of the silicon carbide layer. The silicon carbide layer includes: a body region having a first conductivity type and facing a gate electrode with the gate insulating film being interposed therebetween; and a pair of regions separated from each other by the body region and having a second conductivity type. The body region has an impurity density of 5×1016 cm?3 or greater. This allows for an increased degree of freedom in setting a threshold voltage while suppressing decrease of channel mobility.

Abstract: An IGBT includes a groove provided in a silicon carbide semiconductor layer, a body region of a first conductivity type provided in the silicon carbide semiconductor layer, and an insulating film covering at least a sidewall surface of the groove, the sidewall surface of the groove being a surface having an off angle of 50° or more and 65° or less with respect to a {0001} plane, the sidewall surface of the groove including a surface of the body region, the insulating film being in contact with at least the surface of the body region at the sidewall surface of the groove, and a first conductivity type impurity concentration in the body region being 5×1016 cm?3 or more.

Abstract: A semiconductor device includes: a substrate made of silicon carbide and having a main surface having an off angle of not less than ?° and not more than +5° relative to a (0-33-8) plane in a <01-10> direction; a p type layer made of silicon carbide and formed on the main surface of the substrate by means of epitaxial growth; and an oxide film formed in contact with a surface of the p type layer. A maximum value of nitrogen atom concentration is 1×1021 cm?3 or greater in a region within 10 nm from an interface between the p type layer and the oxide film.