<p>PURPOSE: A semiconductor device is provided to improve productivity by comprising various kinds of thin film transistor structures on the same substrate to reduce the number of processes. CONSTITUTION: A first gate electrode(401) and a second gate electrode(101) are formed on a substrate(400) with an insulation surface. A gate insulation layer(403) covers a first gate electrode and a second gate electrode. A metal thin film(470) is formed on the gate insulation layer. A metal thin film is selectively removed by photolithography technology. An oxide semiconductor layer(471) is formed on the metal thin film and the gate insulation layer.</p>
