Method and structure for second spacer formation for strained silicon mos transistors

Abstract

A method for forming a CMOS semiconductor wafer. The method includes providing a semiconductor substrate (e.g., silicon wafer) and forming a dielectric layer (e.g., silicon dioxide, silicon oxynitride) overlying the semiconductor substrate. The method includes forming a gate layer overlying the dielectric layer and patterning the gate layer to form a gate structure including edges. The method includes forming a dielectric layer overlying the gate structure to protect the gate structure including the edges. Preferably, the dielectric layer has a thickness of less than 40 nanometers. The method includes etching a source region and a drain region adjacent to the gate structure using the dielectric layer as a protective layer and depositing silicon germanium material into the source region and the drain region to fill the etched source region and the etched drain region. The method causes a channel region between the source region and the drain region to be strained in compressive mode from at least the silicon germanium material formed in the source region and the drain region. The method includes forming a second protective layer overlying surfaces and performing an anisotropic etching process to form spacer structures to seal the gate structure.