A semiconductor device may include a semiconductor substrate, an insulator film covering a part of an upper surface of the substrate, and a gate electrode opposing the upper surface via the insulator film. In the semiconductor substrate, a drift layer extending through a body layer to the upper surface opposes the gate electrode via the insulator film. The insulator film extends from the upper surface of the semiconductor substrate to an upper surface of the gate electrode by passing between the gate electrode and an upper electrode, and defines an opening at the upper surface of the gate electrode. In a first region being a set of straight lines where each line extends through an opposing surface of the drift layer that opposes the gate electrode perpendicularly to the opposing surface, the insulator film does not exist on the upper surface of the gate electrode.