| 摘要 |
In a method of manufacturing a semiconductor device having first through third MOS transistors, using a first mask (311), wells (313, 314) and first threshold adjustment regions (315, 316) are formed at transistor areas (306n, 308n) for the second and the third MOS transistors in a semiconductor substrate (301). Next, using a second mask (319), second threshold adjustment regions (320, 321) are formed at transistor areas (304n and 308n) for the first and the third MOS transistors. In the transistor area for the third MOS transistor, both of the first threshold adjustment region and the second threshold adjustment region form a third adjustment region. Thus, using the two masks, three thresholds of the MOS transistors are obtained.
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