US Patent 11949015 Mechanisms for growing epitaxy structure of finFET device

A method includes following steps. A semiconductor fin is formed extending from a substrate. A gate structure is formed extending across the semiconductor fin. Recesses are etched in the semiconductor fin. Source/drain epitaxial structures are formed in the recesses in the semiconductor fin. Formation of each of the source/drain epitaxial structures comprises performing a first epitaxy growth process to form a bar-shaped epitaxial structure in one of the recesses, and performing a second epitaxy growth process to form a cladding epitaxial layer cladding on the bar-shaped epitaxial structure. The bar-shaped epitaxial structure has a lower phosphorous concentration than the cladding epitaxial layer.