A semiconductor device includes: a semiconductor substrate having an upper surface and a lower surface; a field effect transistor having a semiconductor layer on the upper surface of the semiconductor substrate, a gate electrode, a drain electrode, and a source electrode; a P-type diffusion region in the semiconductor substrate and extending to the upper surface of the semiconductor substrate; a first N-type diffusion region in the semiconductor substrate and extending t the upper surface of the semiconductor substrate; a first connection electrode connecting the P-type diffusion region to a grounding point; and a second connection electrode connecting the first N-type diffusion region to the gate electrode or the drain electrode. The P-type diffusion region and the first N-type diffusion region constitute a bidirectional lateral diode.