US Patent 11677013 Source/drain epitaxial layers for transistors

The present disclosure is directed to methods for forming source/drain (S/D) epitaxial structures with a hexagonal shape. The method includes forming a fin structure that includes a first portion and a second portion proximate to the first portion, forming a gate structure on the first portion of the fin structure, and recessing the second portion of the fin structure. The method further includes growing a S/D epitaxial structure on the recessed second portion of the fin structure, where growing the S/D epitaxial structure includes exposing the recessed second portion of the fin structure to a precursor and one or more reactant gases to form a portion of the S/D epitaxial structure. Growing the S/D epitaxial structure further includes exposing the portion of the S/D structure to an etching chemistry and exposing the portion of the S/D epitaxial structure to a hydrogen treatment to enhance growth of the S/D epitaxial structure.