| abstract |
One of the problems of the present invention is to provide a highly reliable semiconductor device by imparting stable electrical characteristics to a transistor using an oxide semiconductor film. In a semiconductor device including an inverted staggered transistor provided on a bottom gate structure on a substrate having an insulating surface, at least a first gate insulating film and a second gate are disposed between the gate electrode layer and the oxide semiconductor film The electrode insulating film is subjected to heat treatment at 450 ° C or higher, preferably 650 ° C or higher, and then an oxide semiconductor film is formed. By performing heat treatment at 450 ° C or higher, preferably 650 ° C or higher, before the formation of the oxide semiconductor film, it is possible to suppress diffusion of hydrogen into the oxide semiconductor film, which is a cause of deterioration or variation in electrical characteristics of the transistor. Therefore, it is possible to impart stable electrical characteristics to the transistor. |