A semiconductor device includes a semiconductor layer on a substrate, a gate electrode electrically insulated from the semiconductor layer by a gate insulating layer, an insulating layer on the gate insulating layer and on the gate electrode, and a source electrode and a drain electrode on the insulating layer, the source and drain electrode being connected to the semiconductor layer. The source electrode overlaps at least a part of the gate electrode. The source electrode, the insulating layer, and the gate electrode overlap each other so as to provide a capacitor.