A semiconductor device includes a semiconductor constituent having a semiconductor substrate and a plurality of electrodes for external connection provided under the semiconductor substrate. An under-layer insulating film is provided under and around the semiconductor constituent. A plurality of under-layer wires are provided under the under-layer insulating film and electrically connected to the electrodes for external connection of the semiconductor constituent. An insulating layer is provided around the semiconductor constituent and on the under-layer insulating film. A frame-like insulating substrate is embedded in an upper surface of the insulating layer and positioned around the semiconductor constituent. A plurality of upper-layer wires are provided on the insulating substrate. A base plate on which the semiconductor constituent and the insulating layer are mounted is removed.