| 摘要 |
There is provided a method of fabricating a semiconductor device, including the steps of (a) forming first well regions in a semiconductor substrate in all regions in which high-voltage and low-voltage MOS transistors are to be formed, the semiconductor At e having a first conductivity and the first well regions having a second conductivity, (b) forming an isolation layer on the semiconductor substrate for isolating the first well regions from each other, (c) forming high-voltage well regions having a first conductivity and low-voltage well regions one of which has a first conductivity and another of which has a second conductivity, and (d) forming MOS transistors on the high-voltage and low-voltage well regions. The high-voltage and low-voltage well regions are formed with the isolation layer being used as a mark. The above-mentioned method makes it possible to form low-voltage and high-voltage MOS transistors on a common semiconductor substrate in the smallest number of fabrication steps.
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