A semiconductor device includes a first circuit substrate having a plurality of lower wiring lines and a plurality of upper wiring lines on the lower surface side and upper surface side thereof, respectively. A second circuit substrate is provided on a lower side of the first circuit substrate, the second circuit substrate having an opening which exposes part of the first circuit substrate, the second circuit substrate also having, on the lower surface side thereof, a plurality of external-connection connection pads and a plurality of test connection pads connected to the lower wiring lines. A first semiconductor construct is disposed on the lower side of the first circuit substrate within the opening of the second circuit substrate, the first semiconductor construct having a plurality of external connection electrodes connected to the lower wiring lines. A third circuit substrate and/or an electronic component is provided on an upper side of the first circuit substrate and connected to the upper wiring lines.