According to one embodiment, a semiconductor device includes a supporter including a first surface, first, second, and third conductive parts, a semiconductor region, and an insulating part. A first direction from the first toward second conductive part is along the first surface. The semiconductor region includes first, second, and third partial regions. A second direction from the first toward second partial region is along the first surface and crosses the first direction. The third partial region is between the first partial region and the second conductive part in the first direction. The third partial region includes a counter surface facing the second conductive part. A direction from the counter surface toward the third conductive part is along the second direction. The insulating part includes an insulating region. At least a portion of the insulating region is between the counter surface and the third conductive part.