| 摘要 |
PROBLEM TO BE SOLVED: To improve reliability in a gate insulating film, and to improve the characteristics of a MOS transistor in a semiconductor integrated circuit device having a plurality of gate insulating films having a different film thickness. SOLUTION: A photoresist layer 9 is selectively formed on an SiO<SB>2</SB>film 8 at a first region R1 and a third region R3, and the SiO<SB>2</SB>film 8 at a second region R2 is removed by etching. Then, after removing the photoresist layer 9, a silicon substrate 1 is thermally oxidized and an SiO<SB>2</SB>film 8b that is thinner than a first gate insulating film 8a is formed at the second region R2. Then, the SiO<SB>2</SB>film 8b at the third region R3 is removed by etching. After removing the photoresist layer 10, the silicon substrate 1 is thermally oxidized, and an SiO<SB>2</SB>film 8c that is thinner than the second gate insulating film 8b is formed at the third region R3. COPYRIGHT: (C)2006,JPO&NCIPI
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