A semiconductor chip 6 is mounted on a flexible substrate 1 wherein internal connecting electrodes 4 to be connected to protruding electrodes 7 on an element surface of the semiconductor chip 6 and wires 3 for connecting the internal connecting electrodes 4 and the external connecting electrodes to be connected to external devices are provided on a surface of an insulating film 2. The internal connecting electrodes 4, the wires 3 and the surface of the insulating film 2 are coated with a protective film 5. The protruding electrodes 7 and the internal connecting electrodes 4 are connected by arranging the element surface of the semiconductor chip 6 to face the flexible substrate 1 and causing the protruding electrodes 7 on the element surface to pierce the protective film 5. This semiconductor device manufacturing method makes it possible to prevent ion migration and reduce occurrence of short circuit between wires.