| CPC H10D 30/0243 (2025.01) [H10D 30/6211 (2025.01); H10D 84/013 (2025.01); H10D 84/0158 (2025.01); H10D 84/038 (2025.01); H10D 30/797 (2025.01)] | 20 Claims |
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1. A method, comprising:
depositing a top epitaxial layer directly on a top surface a substrate using molecular beam epitaxy (MBE) or vapor phase deposition (VPE);
forming a first fin structure and a second fin structure from the top epitaxial layer and a portion of the substrate such that each of the first fin structure and the second fin structure comprises a lower portion made out of the substrate and an upper portion made of the top epitaxial layer;
depositing a dielectric material over the substrate, the first fin structure and the second fin structure;
etching back the dielectric material to form an isolation feature having a first portion disposed between the first fin structure and the second fin structure and a second portion not disposed between the first fin structure and the second fin structure, a top surface of the first portion being higher than a top surface of the second portion;
recessing source/drain regions of the first fin structure and the second fin structure to form a source/drain recess that extends into and terminates in the top epitaxial layer;
conformally depositing a semiconductor layer over surfaces of the source/drain recess;
etching back the semiconductor layer to form a diffusion stop layer over a bottom surface of the source/drain recess,
depositing a first epitaxial layer over the diffusion stop layer and sidewalls source/drain recess;
depositing a second epitaxial layer over the first epitaxial layer; and
depositing a third epitaxial layer over the second epitaxial layer,
wherein the top epitaxial layer comprises a first germanium concentration, the diffusion stop layer comprises a second germanium concentration and the first epitaxial layer comprises a third germanium concentration,
wherein the second germanium concentration is greater than the first germanium concentration or the third germanium concentration.
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