PURPOSE: To include a protective diode in a transistor element by using a comparatively small area, by a method wherein the anode diffusion layer of a diode is formed in the emitter diffusion layer of a transistor, and a protective diode is constituted.

CONSTITUTION: When a backward bias is applied across the base-emitter of a transistor, a current flows firstly to the earth potential through a resistor formed by an N-type emitter diffusion layer 7 of a transistor just under a P-type anode diffusion layer 8 of a protective diode. When the voltage drop becomes higher than the forward voltage of the diode, the PN junction of the diode turns to the forward bias, and the current is absorved through the diode, so that the transistor is protected. In this manner, by forming the layer 8 of a protective diode in the layer 7 of a transistor, connecting them by using a wiring metal layer 10, forming a contact window as the cathode of the diode on the surface of the layer 7 across the layer 8 from a contact window of the layer 7, and forming a wiring metal layer 11, a protective diode can be included in a transistor element, by using a comparatively small area.