A semiconductor device includes an oxide semiconductor layer above an insulating surface, a source electrode in contact with a side surface of the oxide semiconductor layer, a drain electrode in contact with a side surface of the oxide semiconductor layer, a gate insulating film above the oxide semiconductor layer, the source electrode, and the drain electrode, and, a gate electrode overlapping with the oxide semiconductor layer interposed by the gate insulating film. The gate electrode is arranged above and outside of the source electrode and the drain electrode.