Methods for forming super-steep diffusion region profiles in mos devices and resulting semiconductor topographies

Abstract

Methods for fabricating diffusion regions having steep concentration profiles within MOS devices while minimizing junction capacitance degradation are provided. In particular, methods are provided which include patterning a gate structure upon a semiconductor substrate and subsequently etching a recess in exposed portions of the substrate. In some cases, the method includes forming a first dopant region within the exposed portions prior to etching the recess. The method may additionally or alternatively include implanting a second set of dopants into portions of the semiconductor substrate bordering the recess. In either case, the method includes growing an epitaxial layer within the recess and implanting a third set of dopants into the semiconductor topography to form a second dopant region extending to a depth at least within the epitaxial layer. A resulting semiconductor topography includes a source/drain region comprising an upper portion consisting essentially of first dopants of a first conductivity type.