Patent ID: 8441070

Claim:
A semiconductor device comprising: a substrate having a first conductivity-type semiconductor layer in the surface layer; a first first-conductivity-type high-concentration diffusion layer, formed in the surface layer of the first conductivity-type semiconductor layer, which has a higher impurity concentration than that of the first conductivity-type semiconductor layer; a first second-conductivity-type high-concentration diffusion layer, formed in the surface layer of the first conductivity-type semiconductor layer, which electrically contacts with the first first-conductivity-type high-concentration diffusion layer and the first conductivity-type semiconductor layer; a second conductivity-type low-concentration drift layer, formed in the surface layer of the first conductivity-type semiconductor layer, which has a lower impurity concentration than that of the first second-conductivity-type high-concentration diffusion layer; a gate insulating film formed so as to cover the surface of the first conductivity-type semiconductor layer between the first second-conductivity-type high-concentration diffusion layer and the second conductivity-type low-concentration drift layer, and a portion of the second conductivity-type low-concentration drift layer; a gate electrode formed over the gate insulating film; a second first-conductivity-type high-concentration diffusion layer formed in the surface layer of the second conductivity-type low-concentration drift layer; a second conductivity-type sinker layer provided so as to surround the second conductivity-type low-concentration drift layer, the first second-conductivity-type high-concentration diffusion layer ( 106 ), and the first first-conductivity-type high-concentration diffusion layer, when seen in a plan view; and an insulating layer located under the second conductivity-type sinker layer and the first conductivity-type semiconductor layer, wherein a side surface and a bottom surface of the first conductivity-type semiconductor layer is surrounded by the second conductivity-type sinker layer and the insulating layer, and the second conductivity-type sinker layer is electrically connected to the second first-conductivity-type high-concentration diffusion layer.