PURPOSE: To obtain a semiconductor device capable of preventing the secondary breakdown without an increase in the number of parts by forming a transistor and a a rush current protective Zener diode on a same semiconductor substrate.

CONSTITUTION: An N- epi-layer 3 is used for the collector layer of a transistor 1 and the cathode layer of a Zener diode 2 and is connected with a collector electrode 5 through an N+ substrate 4, and the emitter layer 6 of the transistor 1 and the P+ anode layer 7 of the Zener diode 2 are connected with an emitter electrode 8. And the N+ cathode layer 9 is formed in the P+ anode layer 7 of the Zener diode 2 and also in the periphery, at the junction of which the Zener breakdown is brough about, but the N+ cathode layer 9 extending on the transistor 1 side acts as a surface N+ channel stopper since the N epi-layer 3 is inverted at the boundary of the N+ epi-layer 3 with SiO2 10. Therefore, when an L-load is applied, the secondary failure at the ON-OFF period of time may be prevented without an increase in the number of parts.