The invention restrains malfunction of a device caused by back electromotive force of a load containing a component of an inductance L. This device comprises an epitaxial layer formed on a P-type silicon substrate, a P+ diffusion layer 3 that insolates the epitaxial layer into an N- epi-layer 4 of an element formation region and an N- epi-layer 2 of an ineffective region, and an aluminum wiring 6 that electrically connects the N- epi-layer 2 of the ineffective region and the P+ diffusion layer 3. Since an electric potential of the N- epi-layer 2 of the ineffective region can be made equal to that of the P+ diffusion layer 3, even when electrons are injected into the element formation region by the back electromotive force of the load of the inductance L, supplying of the electrons from the P+ diffusion layer 3 to the ineffective region is restrained. |