| 摘要 |
PROBLEM TO BE SOLVED: To form high-quality gate insulating films of different film types on the surface of the same semiconductor substrate easily and highly accurately under high reproducibility. SOLUTION: A device separation area 2 is formed on the surface portion of a silicon substrate 1, a silicon oxide film 3 is formed on the surface of the substrate, and the surface of the silicon oxide film 3 is modified by plasma nitrization to be a nitride layer 4. A resist mask 5 is used as an etching mask to selectively remove the silicon oxide film 3, and the surface of the silicon substrate 1 in that area is exposed. Continuously, the resist mask 5 is removed, the surface of the silicon substrate 1 is washed, a natural oxide film 6 that is produced during the washing step is wet-etched by using diluted fluoric acid, the surface of the silicon substrate 1 is then thermally oxidized and nitrized in the atmosphere of NO gases, and a silicon oxide/nitride film is formed in the exposed area of the silicon substrate 1 as a first gate insulating film. The silicon oxide film 3 is then defined as a second gate insulating film. COPYRIGHT: (C)2005,JPO&NCIPI
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