PURPOSE: To enable to obtain the semiconductor device having a sufficient capacity by a method wherein, in the semiconductor device with which a constant substrate voltage will be given to a semiconductor substrate, a smoothing capacitor is formed on the back side of a chip, thereby unnecessitating the area on the chip.

CONSTITUTION: Substrate voltage is applied to a semiconductor substrate 5 from the substrate voltage generating circuit formed on the surface of a chip, reference voltage is applied to a conductive layer 7 by the wiring located outside the chip, and a capacitor of the desired capacity is formed between said substrate voltage and the reference voltage. An oxide film or other insulating film can be used as an insulating film 6, and a conductive layer such as a polycrystalline silicon layer and the like can be used as a conductive layer 7.