| CPC H10D 64/017 (2025.01) [H01L 21/0214 (2013.01); H01L 21/02211 (2013.01); H01L 21/0228 (2013.01); H01L 21/02323 (2013.01); H01L 21/02337 (2013.01); H01L 21/02343 (2013.01); H10D 64/01 (2025.01); H10D 64/671 (2025.01); H10D 30/024 (2025.01)] | 20 Claims |

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1. A method of forming a semiconductor device, comprising:
forming a sacrificial gate structure over a substrate;
depositing a spacer layer on the sacrificial gate structure in a conformal manner;
performing a multi-step oxidation process to the spacer layer;
etching the spacer layer to form gate sidewall spacers on opposite sidewalls of the sacrificial gate structure;
removing the sacrificial gate structure to form a trench between the gate sidewalls spacers; and
forming a metal gate structure in the trench.
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