| CPC H01L 21/28008 (2013.01) [H01L 21/3065 (2013.01); H01L 21/67069 (2013.01); H10B 41/27 (2023.02); H10B 43/27 (2023.02)] | 5 Claims |

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1. A method for fabricating a semiconductor device comprising:
providing a substrate, in which a first oxide film, a nitride film, and a second oxide film are sequentially stacked, the substrate further comprising a trench penetrating the first oxide film, the nitride film, and the second oxide film in a thickness direction perpendicular to an upper surface of the substrate;
chamfering the first and second oxide films exposed by the trench to reduce the thickness of ends of the first and second oxide films while removing a part of the nitride film exposed by the trench by using a first plasma process, wherein the first plasma process uses a fluorine-containing radical; and
removing a portion of the nitride film left after the first plasma process by using a second plasma process,
wherein a selection ratio of the nitride film to the first and second oxide films is a first selection ratio in the first plasma process,
wherein a selection ratio of the nitride film to the first and second oxide films is a second selection ratio greater than the first selection ratio in the second plasma process.
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