A speaker unit is realized which directly drives a vibration plate having a low density, light weight, yet sufficient rigidity with a digital audio signal, and can thereby transmit vibration of a voice coil thereof to a carbonaceous acoustic vibration plate without loss. An electrical component is fabricated in the silicon layer over a portion of the silicon oxide layer, and then the substrate opposite from the component is masked and etched. A first logical disk and a second logical disk paired with the first logical disk, and each pair belongs to either a first copy group or a second copy group.