A semiconductor device includes a semiconductor substrate; an aluminum electrode disposed on the substrate; a protection film disposed on the aluminum electrode; an opening disposed on the protection film for exposing the aluminum electrode; and a metal electrode disposed on a surface of the aluminum electrode through the opening. The aluminum electrode includes a concavity disposed under the opening. The aluminum electrode disposed at the concavity has a thickness equal to or larger than a depth of the concavity. The surface of the aluminum electrode includes multiple concavities and multiple convexities.