| CPC H10D 62/118 (2025.01) [H10D 30/031 (2025.01); H10D 30/6713 (2025.01); H10D 30/6735 (2025.01); H10D 64/021 (2025.01)] | 20 Claims |

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1. A semiconductor device structure, comprising:
nanostructures formed over a substrate;
a gate structure formed over and around the nanostructures;
a spacer layer formed over a sidewall of the gate structure over the nanostructures;
a source/drain epitaxial structure comprising an edge portion interfacing sidewalls of the nanostructures and a center portion over the edge portion;
a contact structure formed over the source/drain epitaxial structure; and
an air spacer disposed directly over the source/drain epitaxial structure and between the spacer layer and the contact structure,
wherein the edge portion and the center portion are doped and a dopant concentration in the edge portion is smaller than a dopant concentration in the center portion,
wherein the air spacer continuously and vertically extends into the source/drain epitaxial structure such that a portion of the edge portion and a portion of the center portion are exposed in the air spacer.
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