PURPOSE: To enable to adjust the withstand voltage to an arbitrary value less than the junction withstand voltage by prevention of a high withstand voltage transistor incorporated in a complementary type semiconductor device by a method wherein an impurity diffused region of one conductivity type is provided in a well of reverse conductivity type to that of a substrate, and then a diode is constructed between the well and the substrate.

CONSTITUTION: The well 12 of reverse conductivity type to that of the semiconductor substrate 11 of one conductivity type, and the diffused layers 13 and 14 are provided in the substrate. The diffused layer 14 is of reverse conductivity type to that of the well, goes inside the boundary of the well, and exists in electrically floating state at a high concentration. The diffused layer 13 connects to the well at the same potential but has difference in impurity concentration, and the diffused layer 15 connects to the substrate at the same potential but has difference in impurity concentration; thus constructing the P-N junction diode between the well and the substrate. The withstand voltage can be determined by arbitrary selection of the distance l1 from the well end to the diffused layer 15 and the distance l2 to the diffused layer 14 based on the determination of characteristics.