A new film formation method that makes it possible to form a film with a little concentration of contaminants from a material and to form a film on a low heat-resistant member is proposed. Further, a method for forming a film that can keep semiconductor properties is proposed. In the film formation method of the present invention, a first film that is to be a target is formed by employing plasma CVD, and the first film is sputtered, thereby forming the second film on a surface of the substrate to be processed in one chamber. By employing the film formation method of the present invention for a protective film of a semiconductor element, deterioration of a semiconductor device can be controlled.