According to one embodiment, a semiconductor device includes a first electrode, a second electrode, a third electrode, a first conductive member, a first semiconductor layer, a second semiconductor layer, and an insulating member. The third electrode is between the first electrode and the second electrode. The first conductive member is electrically connected to the first electrode. The first conductive member is between the third electrode and the second electrode. The first semiconductor layer includes Alx1Ga1−x1N and includes first, second, third, fourth, and fifth partial regions. The second semiconductor layer includes Alx2Ga1−x2N and includes a first semiconductor region and a second semiconductor region. The insulating member includes first, second, third, fourth, and fifth insulating regions. The first insulating region is between the third partial region and the third electrode. The second insulating region is between the fifth partial region and the first conductive member.