Patent attributes
Homogeneity and stability of electric characteristics of a thin film transistor included in a circuit are critical for the performance of a display device including said circuit. An object of the invention is to provide an oxide semiconductor film with low hydrogen content and which is used in an inverted staggered thin film transistor having well defined electric characteristics. In order to achieve the object, a gate insulating film, an oxide semiconductor layer, and a channel protective film are successively formed with a sputtering method without being exposed to air. The oxide semiconductor layer is formed so as to limit hydrogen contamination, in an atmosphere including a proportion of oxygen. In addition, layers provided over and under a channel formation region of the oxide semiconductor layer are formed using compounds of silicon, oxygen and/or nitrogen.
