| 摘要 |
A mask material layer 102 of a desired pattern is formed on a silicon oxide film 101 . The exposed parts of the silicon oxide film 101 is etched in accordance with the pattern of the mask material layer 102 by plasma etching by using a mixed gas fed at a rate such that the ratio (C<SUB>5</SUB>F<SUB>8</SUB>+O<SUB>2</SUB>/Ar) of the total flow rate of C<SUB>5</SUB>F<SUB>8</SUB>+O<SUB>2 </SUB>to the flow rate of Ar is 0.02 (2%) or less. Thus, a generally vertical right-angled portion is formed in the silicon oxide film 101 . Therefore, no microtrenches are formed, and etching into a desired pattern is precisely effected.
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