According to one embodiment, a semiconductor device includes a first electrode, a second electrode, a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type, an insulating region, and a third semiconductor region of the first conductivity type. The first semiconductor region is provided between the first electrode and the second electrode, and is in contact with the first electrode. The second semiconductor region is provided between the first semiconductor region and the second electrode. The second semiconductor region is in contact with the second electrode. The insulating region extends in a direction from the second electrode toward the first semiconductor region. The insulating region is in contact with the second electrode. The third semiconductor region is provided between the second semiconductor region and the insulating region.