A semiconductor device has: a first transparent electrode, a drain electrode, and a source electrode formed on a substrate; an oxide layer joined electrically to the source electrode and the drain electrode and containing a semiconductor region; an insulating layer formed on the oxide layer and the first transparent electrode; a gate electrode formed on the insulating layer; and a second transparent electrode formed so as to overlap at least a part of the first transparent electrode with the insulating layer interposed therebetween. The oxide layer and the first transparent electrode are formed of the same oxide film.