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 1.times.10.sup.20 /cm.sup.3 to
1.times.10.sup.21 /cm.sup.3 and containing fluorine at a concentration of
1.times.10.sup.15 /cm.sup.3 to 1.times.10.sup.17 /cm.sup.3.
