This invention disclose an amorphous silicon semiconductor film containing at least hydrogen, carbon and oxygen as impurities and the method to produce it. The film is characterized in that the total quantity of carbon and oxygen in said film is at least 0.1 atom %. Since the film has small light absorption coefficient and its optical refractive index is controllable, an excellent window material for solar cell can be provided. Since adherence of the film with a metal electrode as well as with a transparent electrode is sufficient, good reproducibility in making solar cells using the film of this invention as a window material was realized.
