Patent ID: 8227901

Claim:
A mesa type semiconductor device comprising: a semiconductor substrate of a first general conductivity type; a first semiconductor layer of the first general conductivity type disposed on the semiconductor substrate, an impurity concentration of the first semiconductor layer being lower than an impurity concentration of the semiconductor substrate; a second semiconductor layer of a second general conductivity type disposed on the first semiconductor layer so as to form a PN junction between the first and second semiconductor layers; a mesa groove penetrating into the semiconductor substrate through the first and second semiconductor layers; a first insulation film disposed on the second semiconductor layer so that an edge portion of the first insulation film overhangs the mesa groove, the first insulation film not extending into the mesa groove so far as to reach the first semiconductor layer; and a second insulation film disposed on a sidewall of the mesa groove and hanging from the overhanging first insulation film, wherein the overhanging edge portion of the first insulation film has a bottom surface facing the second semiconductor layer and a top surface opposite from the bottom surface, and the second insulation film is in contact with both the top surface and the bottom surface of the first insulation film.