A semiconductor device includes first and second electrodes disposed apart from each other on a substrate, a gate electrode disposed so as to face the first and second electrodes and to cover at least part of each of the first and second electrodes, a semiconductor layer disposed between the first and second electrodes and the gate electrode, and a gate insulating layer disposed between the gate electrode and the semiconductor layer, the gate insulating layer having a film thickness that is greater in portions located directly above areas where the first and second electrodes are under the gate electrode than in a portion located directly above an area between the first and second electrodes.