Patent ID: 7061047

Claim:
A semiconductor device comprising: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type formed on a main surface of the first semiconductor layer; a third semiconductor layer of the first conductivity type formed in the second semiconductor layer and electrically isolated from the first semiconductor layer; a trench formed to extend from the surface of the third semiconductor layer and penetrate the third semiconductor layer and having depth to reach at least a portion lying near the first semiconductor layer; a first insulating film formed on side walls and a bottom portion of the trench; a first electrode formed at least partly on the first insulating film in the trench and electrically isolated from the first to third semiconductor layers; and a fourth semiconductor layer of the first conductivity type formed near the trench on an interface between the first and second semiconductor layers and having an impurity concentration higher than that of the first semiconductor layer, wherein an impurity concentration profile of a part, formed along and directly facing a side surface of the trench, of the second semiconductor layer has a first peak and a second peak.