PURPOSE: To prevent internal circuit damage clue to abnormal voltage like static electricity and improve protective function, for both the part between an I/O signal terminal and an earth electrode and the part between the I/O signal terminal and a power supply electrode (semiconductor substrate), without increasing the occupied area of a protective element.

CONSTITUTION: A P-type well part 3 under a collector region 6 of one bipolar transistor type protective element constituted of a base region 4, an emitter region 5, and a collector region 6 is shallowly formed, and the other bipolar transistor type protective element wherein the shallow part is made the base region is constituted. The collector region 6 is connected with an I/O signal terminal 10, and an N-type semiconductor substrate 1 is connected with a power supply terminal 9. Thereby the internal circuit 8 is protected from an abnormal voltage due to static electricity or the like generated between the I/O terminal 10 and the power supply terminal 9.