Protective device for integrated circuit.

摘要

For a protection of an integrated circuit fabricated on a semiconductor substrate (31) of a first conductivity type against excess voltages applied thereto, there is disclosed a protective device comprising a first impurity region (33) of a second conductivity type formed in a surface portion of the semiconductor substrate and electrically connected to a termina plate (32) which supplies the integrated circuit with normal external voltages, and a second impurity region (34) of the second conductivity type formed in the surface portion of the semiconductor substrate and electrically connected to a voltage supply layer (36) to which a difference voltage is applied, the second impurity region being electrically insulated from the first impurity region under the normal external voltages, a current path being established between the first and second impurity regions under an application of an abnormal external voltages applied through the terminal plate.