A semiconductor device according to the present embodiment includes a semiconductor substrate, an insulating film and a conductive film. The insulating film is disposed on a first surface of the semiconductor substrate. The insulating film covers a semiconductor element. The conductive film penetrates the semiconductor substrate across from the first surface to a second surface opposite to the first surface. On the second surface, a trench continuously or intermittently exists across from a first end part side of the second surface to a second end part side thereof.