According to one embodiment, a semiconductor device includes a base layer, a second conductivity type semiconductor layer, a first insulating film, and a first electrode. The first insulating film is provided on an inner wall of a plurality of first trenches extending from a surface of the second conductivity type semiconductor layer toward the base layer side, but not reaching the base layer. The first electrode is provided in the first trench via the first insulating film, and provided in contact with a surface of the second conductivity type semiconductor layer. The second conductivity type semiconductor layer includes a first second conductivity type region, and a second second conductivity type region. The first second conductivity type region is provided between the first trenches. The second second conductivity type region is provided between the first second conductivity type region and the base layer, and between a bottom part of the first trench and the base layer. The second second conductivity type region is smaller in a quantity of second conductivity type impurities than the first second conductivity type region.