| CPC H01L 21/31155 (2013.01) [H01L 21/02532 (2013.01); H01L 21/0259 (2013.01); H10D 30/024 (2025.01); H10D 30/031 (2025.01); H10D 30/6713 (2025.01); H10D 30/6735 (2025.01); H10D 30/6757 (2025.01); H10D 30/792 (2025.01); H10D 62/021 (2025.01); H10D 62/118 (2025.01); H10D 64/017 (2025.01); H10D 64/018 (2025.01); H10D 64/021 (2025.01); H10D 84/0147 (2025.01); H10D 84/038 (2025.01)] | 20 Claims |

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18. A method, comprising:
forming a dummy gate stack over a channel region of an active region, the dummy gate stack comprising:
a dummy electrode comprising polysilicon and a necking portion, and
a spacer layer disposed along sidewalls of the dummy electrode;
forming a source/drain feature over a source/drain region of the active region;
depositing a contact etch stop layer (CESL) to interface a sidewall of the spacer layer and a top surface of the source/drain feature;
depositing a dielectric layer over the CESL;
planarizing the dielectric layer to expose the spacer layer and the dummy electrode;
after the planarizing, implanting germanium into the dielectric layer, the spacer layer and the dummy electrode;
after the implanting, annealing the dummy electrode to widen the necking portion; and
after the annealing, replacing the dummy gate stack with a metal gate stack,
wherein the metal gate stack comprises titanium aluminum.
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