Semiconductor device structure and methods of forming the same

Abstract

A semiconductor device structure and methods of forming the same are described. The method includes forming a fin structure over a substrate, forming a sacrificial gate structure on a portion of the fin structure, and recessing an exposed portion of the fin structure to form a source / drain recess. The exposed portion of the fin structure is recessed by a cyclic etching process, the cyclic etching process includes performing a plurality of cycles, and each cycle includes a plasma formation stage, an etch stage, and a purge stage. A shape of the source / drain recess is controlled by adjusting a ratio of a time duration of the purge stage to a time duration of the plasma formation and etch stages.

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