According to an embodiment, a semiconductor device includes a first electrode, a first semiconductor region of a first conductivity type, second semiconductor regions of a second conductivity type, a third semiconductor region of the second conductivity type, a fourth semiconductor region of the first conductivity type, a fifth semiconductor region of the second conductivity type, a gate electrode, and a second electrode. The first semiconductor region is provided on the first electrode. The first semiconductor region includes first portions and first protruding portions. The first portions are arranged along a first direction and a second direction perpendicular to the first direction. The first protruding portions respectively protrude from the first portions. The second semiconductor regions are spaced from each other and provided in the first semiconductor region. The third semiconductor region is provided on the first semiconductor region and the second semiconductor regions.