| 摘要 |
To provide an etching method for broadening a trench opening between patterns of an etching mask in a dry process. The etching method of a semiconductor substrate in which silicon and a silicon nitride film are exposed at least on a surface of the semiconductor substrate, comprises an oxidation step of oxidizing the silicon and the silicon nitride film from an exposed surface to a given film thickness by spraying the semiconductor substrate with substances excited by plasma discharge of O<subscript>2 </highlight>gas as a reaction gas, and an etching step of etching the semiconductor substrate oxidized in the oxidation step by plasma using a reaction gas comprising at least O<subscript>2 </highlight>gas and CH<subscript>2</highlight>F<subscript>2 </highlight>gas.
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