Silicon carbide semiconductor element

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;
• a second electrode which is arranged on the back surface of the semiconductor substrate;
• and
• a channel layer of the first conductivity type,
• 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 the channel layer is arranged between the first and second side surfaces of the trench and the gate insulating film,
• wherein a portion of the channel layer which contacts with a part of the body region that is exposed on the first side surface is thicker than another portion of the channel layer which contacts with another 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.