| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device structure, where a wafer process can be set up quickly, keeping the device high in resistance and fine in structure, and transistors of different operating voltages are mounted mixedly. SOLUTION: Gates 3A to 3C and gate oxide films 31A to 31C are each set larger in length and thickness, with increase in operating voltage, a high-voltage transistor TC is enhanced in resistance restraining the electric field of a channel, and a low-voltage transistor TA is subminiaturized in size, according to a low operating voltage. Impurity concentration is set lower than 4×1018×(VCCmax)-1.6 [cm-3] (VCCmax: maximum operating voltage) at the base of a junction of a well 11 with a source 13 and a drain 14 respectively, while keeping a semiconductor device high in resistance, the wells 11 are provided identical in all the transistors TA to TC respectively, and impurities injected into the surface of a substrate 100 to control the threshold voltage are set equal in dose for the transistors TA to TC, by which a heat history can be simplified in the formation of impurity regions.
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