A method of manufacturing a semiconductor device forms a penetrating hole in a substrate so that the penetrating hole extends from a first surface of the substrate to a second surface of the substrate being opposite to the first surface. An internal wall surface of the penetrating hole has a protrusion formed of a material constituting the substrate, the first surface of the substrate being closer to the protrusion than the second surface. A conductive member is formed on the first surface so that the conductive member covers the penetrating hole. A semiconductor chip is mounted on the first surface so that an electrode of the semiconductor chip is electrically connected to the conductive member. An external electrode is provided through the penetrating hole so that the external electrode is electrically connected to the conductive member and the external electrode projects from the second surface of the substrate.