According to one embodiment, a semiconductor device includes a nitride semiconductor layer, a first electrode provided on the layer, a second electrode provided on the layer, a insulating film provided on the layer, a first control electrode provided on the film, and a conductor provided on the film. The first control electrode includes a first edge, and a second edge. The first edge is provided between the second edge and the first electrode. The conductor includes a first portion and a third edge positioned between the first portion and the first electrode. An electric field strength at a first region is substantially equal to an electric field strength at a second region. The first region overlaps the first edge when projected onto a plane perpendicular to a stacking direction. The second region overlaps the third edge when projected onto the plane.