A semiconductor device includes a substrate; a layered body formed on the substrate and including a multilayer interconnection structure, the layered body including multiple interlayer insulating films stacked in layers, the interlayer insulating films being lower in dielectric constant than a SiO2 film; a moisture resistant ring extending continuously in the layered body so as to surround a device region where an active element is formed; a protection groove part formed continuously along and outside the moisture resistant ring in the layered body so as to expose the surface of the substrate; a protection film continuously covering the upper surface of the layered body except an electrode pad on the multilayer interconnection structure, and the sidewall and bottom surfaces of the protection groove part; and an interface film including Si and C as principal components and formed between the protection film and the sidewall surfaces of the protection groove part.