Patent ID: 7679143

Claim:
A semiconductor device comprising: a MOS transistor having a drain and a source; a protection diode having a cathode and an anode; and a semiconductor substrate having a N − conductive type, wherein the MOS transistor and the protection diode are disposed in the semiconductor substrate, the drain of the MOS transistor is connected to the cathode of the protection diode, the source of the MOS transistor is connected to the anode of the protection diode, the anode of the protection diode is provided by a P type region disposed in a surface portion of the semiconductor substrate having a N − conductive type, the cathode of the protection diode is provided by a N type region disposed in the surface portion of the semiconductor substrate having a N − conductive type, the N type region is disposed adjacent to the P type region, the surface portion of the semiconductor substrate having a N − conductive type further includes a P + type region and a first N + type region, the P + type region is disposed in the P type region in order to connect to an electrode of the anode, the first N + type region is disposed in the N type region in order to connect to an electrode of the cathode, the semiconductor substrate having an N − conductive type has an SOI construction so that the semiconductor substrate includes an embedded insulation film and an N − type SOI layer, the N − type SOI layer is disposed on the embedded insulation film, the semiconductor substrate further includes a N + type layer, which is disposed between the N − type SOI layer and the embedded insulation film, the surface portion of the semiconductor substrate having an N − conductive type further includes a second N type region, the second N type region is disposed adjacent to the N type region, and the P type region is disposed in the second N type region, the MOS transistor has a withstand voltage defined as V T , the protection diode has a withstand voltage defined as V D , a parasitic resistance defined as R D , and a maximum current defined as I Rmax , the withstand voltage of V T of the MOS transistor and the withstand voltage of V D , the parasitic resistance of R D , and the maximum current of I Rmax of the protection diode satisfy a relationship of V T >V D +I Rmax ×R D , and the maximum current of I Rmax of the protection diode is equal to or larger than 45 Amperes.