| abstract |
In semiconductor devices using oxide semiconductors, electrical characteristics change by irradiating visible light or ultraviolet light. In view of such a problem, it is one of the problems to provide a stable semiconductor device to a semiconductor device using an oxide semiconductor film and to manufacture a highly reliable semiconductor device. A first oxide semiconductor layer having a film thickness of 1 nm or more and 10 nm or less is formed on the oxide insulating layer, crystallized by heat treatment to form a first crystalline oxide semiconductor layer, and thereon, than the first crystalline oxide semiconductor layer. A thick second crystalline oxide semiconductor layer is formed. |