Patent ID: 8686439

Claim:
A silicon carbide semiconductor element comprising: a semiconductor substrate of a first conductivity type; a drift layer of the first conductivity type which is located on the principal surface of the semiconductor substrate; a body region of a second conductivity type which is located on the drift layer; an impurity region of the first conductivity type which is located on the body region; a trench which runs through the body region and the impurity region to reach the drift layer; a gate insulating film which is arranged on surfaces of the trench; a gate electrode which is arranged on the gate insulating film; a first electrode which contacts with the impurity region; and a second electrode which is arranged on the back surface of the semiconductor substrate, wherein the surfaces of the trench include a first side surface and a second side surface which is opposed to the first side surface, wherein a portion of the gate insulating film which is arranged on a part of the body region that is exposed on the first side surface is thinner than another portion of the gate insulating film which is arranged on a part of the body region that is exposed on the second side surface, and wherein the concentration of a dopant of the second conductivity type is higher at least locally in a portion of the body region which is located beside the first side surface than in another portion of the body region which is located beside the second side surface.