Abstract: A semiconductor device having a protective circuit, in order to prevent from breaking internal circuits according to electrostatic forces or noises generated on an input terminal is provided. In the semiconductor, a protective diode for countermeasures is applied to the overshoot between the input terminal and a power source wiring, and a MOS transistor is provided between the power source wiring and a ground wiring. The MOS transistor operates as a gate-controlled lateral transistor and becomes conductive earlier than a large size bipolar transistor resulting in providing protection between the input terminal and the ground wiring.

Abstract: A method of manufacturing a semiconductor device with MOSFETs including the steps of forming an anti-oxidation film pattern over an element forming region of a semiconductor substrate, selectively oxidizing a region not covered with the anti-oxidation film pattern on the semiconductor substrate to form an isolating oxide film, and implanting impurities into the semiconductor substrate via the isolating oxide film and anti-oxidation film at a predetermined acceleration energy to form a threshold voltage control region under the anti-oxidation film and a channel stop region under the isolating oxide film. The channel stop region and threshold voltage control region can be formed by a single ion implantation process.