A method for manufacturing a semiconductor device includes the steps of: forming a trench in a semiconductor substrate; and forming an epitaxial film on the substrate including a sidewall and a bottom of the trench so that the epitaxial film is filled in the trench. The step of forming the epitaxial film includes a final step before the trench is filled with the epitaxial film. The final step has a forming condition of the epitaxial film in such a manner that the epitaxial film to be formed on the sidewall of the trench has a growth rate at an opening of the trench smaller than a growth rate at a position of the trench, which is deeper than the opening of the trench.