A semiconductor device includes a semiconductor component which has a semiconductor substrate provided with an integrated circuit on an under side of the semiconductor substrate and a plurality of external connection electrodes provided on the underside of the semiconductor substrate, and a plurality of interconnections each of which includes one end portion connected to each of the external connection electrodes of the semiconductor component and the other end portion extended outside the semiconductor substrate. An under fill medium is provided to cover at least an underside of the semiconductor substrate and at least the side surfaces of the external connection electrodes. A sealing medium is provided to cover an upper side and a side surface of the semiconductor substrate, and the under fill medium. The undersurface of the under fill medium is flush with the undersurfaces of the interconnections.