Patent ID: 8154074

Claim:
A SiC semiconductor device comprising: a substrate made of SiC and having a first conductive type or a second conductive type; a drift layer made of SiC, having the first conductive type, and disposed on a first side of the substrate; a trench perpendicular to a surface of the drift layer and disposed in the drift layer; a base region having the second conductive type, made of SiC, contacting a sidewall of the trench, and sandwiching the trench; a source region made of SiC, having the first conductive type, contacting the sidewall of the trench, sandwiching the trench, and arranged in an upper portion of the base region; a gate insulation film disposed on an inner wall of the trench; a gate electrode disposed in the trench via the gate insulation film; a source electrode electrically coupled with the source region and the base region; and a drain electrode disposed on a second side of the substrate, wherein the second side is opposite to the first side, a part of the base region contacting the sidewall of the trench provides a channel region so that current flows between the source electrode and the drain electrode via the source region, the channel region and the drift layer when a voltage is applied to the gate electrode, the source region has multi-layered structure including a first layer and a second layer, the first layer as an upper layer contacts the source electrode with ohmic contact, the second layer as a lower layer has an impurity concentration, which is lower than an impurity concentration of the layer, the first layer includes a first impurity having the first conductive type, and the second layer includes a second impurity having the first conductive type, and the second impurity has an atomic radius that is smaller than an atomic radius of the first impurity.