| abstract |
A transistor using an oxide semiconductor having a high field-effect mobility, a small deviation of a threshold voltage, and high reliability is provided. Another object of the present invention is to provide a high-performance semiconductor device which has been difficult to realize by using the transistor. An oxide semiconductor film containing two or more, preferably three or more, elements selected from indium, tin, zinc and aluminum is used for the transistor. The oxide semiconductor film is formed while heating the substrate. In addition, oxygen is supplied to the oxide semiconductor film by an insulating film or / and an ion implantation which are adjacent to each other in the manufacturing process of the transistor, and the oxygen deficiency which becomes a carrier generating source is greatly reduced. Further, in the transistor fabrication process, the oxide semiconductor film is highly purified and the hydrogen concentration is made very low. |