A semiconductor film having a crystalline structure is formed by using a metal element that assists the crystallization of the semiconductor film, and the metal element remaining in the film is effectively removed to decrease the dispersion among the elements. The semiconductor film or, typically, an amorphous silicon film having an amorphous structure is obtained based on the plasma CVD method as a step of forming a gettering site, by using a monosilane, a rare gas element and hydrogen as starting gases, the film containing the rare gas element at a high concentration or, concretely, at a concentration of 1x1020/cm3 to 1x1021/cm3 and containing fluorine at a concentration of 1x1015/cm3 to 1x1017/cm3.