A semiconductor device according to an embodiment includes first and second electrodes, a gate electrode, first to third semiconductor regions, and first and second insulating parts. The first semiconductor region is located on the first electrode. The second semiconductor region is located on the first semiconductor region. The third semiconductor region is located on the second semiconductor region. The first insulating part is arranged with the third semiconductor region, the second semiconductor region, and a portion of the first semiconductor region. The gate electrode is located in the first insulating part. The gate electrode faces the second semiconductor region. The second insulating part is located on the third semiconductor region. The second insulating part is not overlapping the gate electrode. The second insulating part has tensile stress. The second electrode is located on the second insulating part and electrically connected with the third semiconductor region.