A photolithography process for forming an island-shaped semiconductor layer is omitted, and a transistor is formed by at least two photolithography processes: a photolithography process for forming a gate electrode (including a wiring or the like formed from the same layer as the gate electrode) and a photolithography process for forming a source electrode and a drain electrode (including a wiring or the like formed from the same layer as the source electrode and the drain electrode). By using electron beam exposure, a transistor in which a distance between the source electrode and the drain electrode (channel length) is short can be formed. For example, a transistor whose channel length is less than 50 nm can be obtained.