| abstract |
A transistor using an oxide semiconductor having high field-effect mobility, small variation in threshold voltage, and high reliability is provided. In addition, using the transistor, Provided is a high-performance semiconductor device that has been difficult to realize so far. An oxide semiconductor film containing two or more elements, preferably three or more elements selected from indium, tin, zinc, and aluminum is used for a transistor. The oxide semiconductor film is formed while the substrate is heated. In the manufacturing process of the transistor, oxygen is supplied to the oxide semiconductor film by a nearby insulating film and / or ion implantation, and oxygen vacancies serving as a carrier generation source are reduced as much as possible. In the manufacturing process of the transistor, the oxide semiconductor film is highly purified and the hydrogen concentration is extremely low. [Selection] Figure 1 |