According to one embodiment, a semiconductor device includes first to third electrodes, first and second conductive members, a semiconductor member, and a first insulating member. The first conductive member is electrically connected with the second electrode or is electrically connectable with the second electrode. The semiconductor member includes first to third semiconductor regions. The first semiconductor region includes first to fourth partial regions. The third partial region is between the first and second partial regions. The second semiconductor region is between the third partial region and the third semiconductor region. The fourth partial region is between the third partial region and the second semiconductor region. At least a portion of the second semiconductor region is between the second conductive member and the third electrode. The second conductive member is electrically insulated from the second and third electrodes. The first insulating member includes first to third insulating regions.