PURPOSE: To eliminate the OFF operation of a photodrive type P-N-P-N type semiconductor switch in an external circuit by adding a photodiode circuit capable of forming in a process manner simultaneously upon the first gate electrode onto the same substrate as the switch and providing OFF function due to the optical drive.

CONSTITUTION: Polysilicon P-N junctions a, b are used as a photodiode. An electrode 26 of the junction a is connected to an electrode 27 of the junction b, the electrode 25 of the junction a is further connected to the first gate electrode 30, and the electrode 28 of the junction b is connected to the cathode electrode 32 of a P-N-P-N element. One terminal of a polysilicon resistor 29 formed as a high resistance is connected to the electrode 25 of the junction (a), and the other terminal is connected to the electrode of the junction b. An anode electrode 12 is connected to an anode region 2, and an anode terminal 33 is connected to the electrode 12. The first N type diffused region 35 and the second N type diffused region 36 are fored on the P type gate region 3, the cathode electrode 13 is bonded to the region 35, and the cathode terminal 32 is connected to the electrode 13.