A method for forming crystalline SiC-based regions on either side of an N-type transistor channel, including: providing a substrate including a silicon-based layer having a thickness e, forming at least one masking pattern on the silicon-based layer, with the at least one masking pattern having openings, with the openings corresponding to implantation regions of the silicon-based layer, amorphising the silicon-based layer through the openings of the at least one masking pattern, in the implantation regions, to a depth d strictly less than the thickness e, so as to form amorphised implantation regions in the silicon-based layer, implanting carbon into amorphous implantation regions, performing thermal recrystallisation annealing to turn the amorphised implantation regions into crystalline SiC-based regions, the method including: after forming the crystalline SiC-based regions, forming a transistor gate on the silicon-based layer, directly at the edge of the crystalline SiC-based regions.

A source region of a MOSFET includes a source contact region connected to a source electrode, a source extension region adjacent to a channel region of a well region, and a source resistance control region provided between the source extension region and the source contact region. The source resistance control region includes a low concentration source resistance control region which has an impurity concentration lower than that of the source contact region or the source extension region and a high concentration source resistance control region which is formed between the well region and the low concentration source resistance control region and has an impurity concentration higher than that of the low concentration source resistance control region.

A silicon carbide semiconductor device includes: n type regions formed on a surface of the n.sup.− type epitaxial layer; p type body regions formed at positions deeper than the n type regions; p.sup.− type channel regions each reaching the p type body region; and n.sup.++ type source regions formed toward the p type body region from the front surface side of the epitaxial layer, and the p.sup.− type channel regions and the n.sup.++ type source regions are formed at a planar position where the n type region remains between the p.sup.− type channel region and the n.sup.++ type source region, and out of boundary surfaces which are formed between the p.sup.− type channel region and the n type regions, the boundary surface on an outer peripheral side is positioned inside an outer peripheral surface 116a of the p type body region as viewed in a plan view.

A semiconductor device includes a first electrode, a second electrode, and a silicon carbide layer. The silicon carbide layer includes a first conductivity type first region extending inwardly thereof. The impurity concentration of the first region increases in the depth direction of the silicon carbide layer. The silicon carbide layer includes a second conductivity type second region located adjacent to the first region and containing first and second conductivity type impurities. The concentration of the first conductivity type impurity in the second region increases in the depth direction of the silicon carbide layer. The silicon carbide layer includes a second conductivity type third region. The first region is located between the second region and the third region. The third region contains the first and second conductivity type impurities. The concentration of the first conductivity type impurity in the third region increases in the depth direction of the silicon carbide layer.

An ion implantation mask, which is an inorganic insulating film, is formed on a silicon carbide substrate. A mask portion and two regions of an opened ion implantation portion are formed in the ion implantation mask by dry etching. At that time, a residual portion which is thinner than the mask portion is formed in the bottom of the opened ion implantation portion. Then, ions are implanted through the ion implantation mask to form a predetermined semiconductor region in the silicon carbide substrate. According to this structure, it is possible to prevent an increase in the roughness of the surface of the silicon carbide substrate and to improve breakdown voltage.

Examples of a semiconductor device includes a transistor region formed in a semiconductor substrate having a first conductivity type drift layer, and a diode region formed to be adjacent to the transistor region in the semiconductor substrate, wherein the diode region has a second conductivity type anode layer formed on the drift layer and a first conductivity type cathode layer formed on the lower side of the drift layer, and the cathode layer has an adjacent region contacting the transistor region, the adjacent region having a depth, from a lower surface of the semiconductor substrate, which becomes shallower toward the transistor region and having first conductivity type impurity concentration which decreases toward the transistor region.

A silicon carbide device includes a silicon carbide body with a trench gate structure that extends from a first surface into the silicon carbide body. A body region is in contact with an active sidewall of the trench gate structure. A source region is in contact with the active sidewall and located between the body region and the first surface. The body region includes a first body portion directly below the source region and distant from the active sidewall. In at least one horizontal plane parallel to the first surface, a dopant concentration in the first body portion is at least 150% of a reference dopant concentration in the body region at the active sidewall and a horizontal extension of the first body portion is at least 20% of a total horizontal extension of the body region.

A semiconductor device of an embodiment includes a SiC layer including a first trench, a second trench having first and second regions, an n-type first SiC region, a p-type second SiC region, an n-type third SiC region, a p-type fourth SiC region between the first trench and the first SiC region, and a p-type fifth SiC region between the second trench and the first SiC region and having a first portion and a second portion, a gate electrode in the first trench, a first electrode in the second trench, and a second electrode. A distance between the first trench and the first region is greater than a distance between the first trench and the second region, the first portion is separated from the fourth SiC region, the second portion contacts the fourth SiC region, the first region contacts the first portion, and the second region contacts the second portion.

A semiconductor device (A1) includes a semiconductor layer having a first face with a trench (3) formed thereon and a second face opposite to the first face, a gate electrode (41), and a gate insulating layer (5). The semiconductor layer includes a first n-type semiconductor layer (11), a second n-type semiconductor layer (12), a p-type semiconductor layer (13), and an n-type semiconductor region (14). The trench (3) is formed so as to penetrate through the p-type semiconductor layer (13) and to reach the second n-type semiconductor layer (12). The p-type semiconductor layer (13) includes an extended portion extending to a position closer to the second face of the semiconductor layer than the trench (3) is. Such structure allows suppressing dielectric breakdown in the gate insulating layer (5).

A semiconductor device of an embodiment includes an element region and a termination region surrounding the element region. The element region includes a gate trench, a first silicon carbide region of n-type, a second silicon carbide region of p-type on the first silicon carbide region, a third silicon carbide region of n-type on the second silicon carbide region, and a fourth silicon carbide region of p-type sandwiches the first silicon carbide region and the second silicon carbide region with the gate trench, the fourth silicon carbide region being deeper than the gate trench. The termination region includes a first trench surrounding the element region, and a fifth silicon carbide region of p-type between the first trench and the first silicon carbide region, the fifth silicon carbide region same or shallower than the fourth silicon carbide region. The semiconductor device includes a gate electrode, a first electrode, and a second electrode.