A non-Si non-C-based gas is heated by a thermal catalysis body provided in a gas introduction channel, and the heated non-Si non-C-based gas and a material-based gas comprising Si and/or C are separately introduced into a film deposition space through a showerhead having a plurality of gas effusion ports, and in the film deposition space, a plasma space is formed by a nonplanar electrode connected to a radio frequency power supply, thereby forming a film on a substrate. Formation of high-quality Si-based films and C-based films can thus be accomplished at high deposition rate over large area with uniform film thickness and homogeneous quality. Also, highly efficient devices including photoelectric conversion devices represented by solar cells can be manufactured at low-cost by the use of such films.