| 摘要 |
An impurity for adjusting a threshold voltage is ion-implanted using, as masks, a resist for forming P--type diffusion layers, a resist for forming N+-type diffusion layers and N-type diffusion layers and a resist for forming P+-type diffusion layers and N-type diffusion layers. For this reason, a semiconductor device including first to third N-channel transistors and first and second P-channel transistors, all of which respectively have different threshold voltages, can be manufactured without using an additional resist except for the above resists. Therefore, an operating margin at a low voltage can be improved and data retention characteristics can be improved in a memory without causing an increase in cost, an increase in power consumption and the like.
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