A semiconductor device includes a semiconductor layer, gate electrodes, an insulating film, source electrodes, and drain electrodes which are provided on the semiconductor layer. Each of the source electrodes and the drain electrodes are spaced in the insulating film from a corresponding gate electrode, such that one end thereof is in contact with the semiconductor layer and the other end thereof is exposed. Further, the semiconductor device includes first field plate electrodes, each of which is provided on a corresponding gate electrode and the insulating film, and second field plate electrodes, each of which is provided on the insulating film between a corresponding first field plate electrode and a corresponding drain electrode. Furthermore, the thickness of the insulating film between each first field plate electrode and the semiconductor layer is smaller than the thickness of the insulating film between each second field plate electrode and the semiconductor layer.