Semiconductor device

Trenches each have longer sides extending in a longitudinal direction, and shorter sides linking the longer sides together. The trenches are periodically arranged in the longitudinal direction and a transverse direction. A first region is on a drift layer of a first conductivity type, has a second conductivity type, and is penetrated by the trenches. A second region is on the first region so as to be away from the drift layer, has the first conductivity type, and is in contact with the longer sides of each of the trenches so as to be away from the ends of the longer sides. A third region is on the first region, has the second conductivity type, and has a higher impurity concentration than the first region. The gate electrode is in the trench with a gate insulating film interposed therebetween.