A semiconductor device includes a substrate; a gate electrode provided on the substrate; a first insulating layer formed on the gate electrode; an island-shaped oxide semiconductor layer formed on the first insulating layer; a source electrode electrically connected to the oxide semiconductor layer; and a drain electrode electrically connected to the oxide semiconductor layer, wherein the first insulating layer has a recess in the surface, wherein the oxide semiconductor layer is formed on a bottom surface and side walls of said recess and on an upper face of the first insulating layer, and wherein at least one of the source electrode and the drain electrode is disposed on a portion of the oxide semiconductor layer over the side walls of said recess, and is not formed on a portion of the oxide semiconductor layer over the upper face of the first insulating layer.