According to one embodiment, a semiconductor device includes an insulating substrate, a first metal layer on the insulating substrate, a first insulating layer on the insulating substrate and the first metal layer, a semiconductor layer on the first insulating layer, a second insulating layer on the semiconductor layer and the first insulating layer, a second metal layer on the second insulating layer, and a first electrode and a second electrode which are electrically connected to the semiconductor layer. The first metal layer overlaps the second metal layer. A third metal layer contacts a top surface of the second metal layer and a top surface of the first metal layer.