Transistor fabrication using double etch/refill process

摘要

A semiconductor fabrication process includes forming a gate electrode ( 120 ) overlying a gate dielectric ( 110 ) overlying a semiconductor substrate ( 102 ). First spacers ( 124 ) are formed on sidewalls of the gate electrode ( 120 ). First s/d trenches ( 130 ) are formed in the substrate ( 102 ) using the gate electrode ( 120 ) and first spacers ( 124 ) as a mask. The first s/d trenches ( 130 ) are filled with a first s/d structure ( 132 ). Second spacers ( 140 ) are formed on the gate electrode ( 120 ) sidewalls adjacent the first spacers ( 124 ). Second s/d trenches ( 150 ) are formed in the substrate ( 102 ) using the gate electrode ( 120 ) and the second spacers ( 140 ) as a mask. The second s/d trenches ( 150 ) are filled with a second s/d structure ( 152 ). Filling the first and second s/d trenches ( 130, 150 ) preferably includes growing the s/d structures using an epitaxial process. The s/d structures ( 132, 152 ) may be stress inducing structures such as silicon germanium for PMOS transistors and silicon carbon for NMOS transistors.