Semiconductor device structure and method for forming the same

Abstract

A semiconductor device structure and a method for its formation 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 removing an exposed portion of the fin structure to form a source / drain cavity. The exposed portion of the fin structure is removed by a cyclic etching process, which comprises multiple cycles, each consisting of a plasma generation stage, an etching stage, and a rinse stage. The shape of the source / drain cavity is controlled by adjusting the ratio of the rinse stage duration to the plasma generation and etching stage durations.