Method and apparatus for manufacturing semiconductor device

A method and apparatus for manufacturing a semiconductor device can achieve the formation of thin films in a uniform thickness on a substrate. The method and apparatus includes a film-forming process in which film-forming gases 14, 15 are caused to flow over a surface of a substrate 11 substantially in parallel therewith to form thin films on the substrate surface. The film-forming process includes an initial film-forming step for forming a first thin film on the surface of the substrate 11 under a first film-forming conditions and a main film-forming step for forming, on the first thin film acting as a backing layer, a second thin film of a thickness greater than that of the first thin film under a second film-forming condition which differs from the first film-forming condition.