Patent ID: 8530966

Claim:
A semiconductor device, comprising: a drift layer of a first conductivity type formed on a semiconductor substrate of the first conductivity type; a base layer of a second conductivity type formed selectively in a surface of said drift layer; a well layer of the second conductivity type formed in the surface of said drift layer, the well layer being adjacent to said base layer; a trench extending from a surface of said base layer to a surface of said well layer, the trench having a trench end portion defined in the surface of said well layer and in a direction in which the trench extends; and a gate electrode formed selectively on said drift layer in which said trench is formed, wherein said trench has first and second regions, the first region extending from said trench end portion to get into the surface of said base layer near a boundary between said base layer and said well layer, the second region extending in the surface of said base layer from an end portion of said first region, and a trench width is greater in said first region than in said second region.