Poly Silicon Gate Doping Method and Structure for Strained Silicon MOS Transistors

A method for forming a semiconductor integrated circuit device comprising:

• providing a semiconductor substrate;
• forming a dielectric layer overlying the semiconductor substrate;
• forming a gate layer overlying the dielectric layer, the gate layer being overlying a channel region in the semiconductor substrate;
• forming a hard mask overlying the gate layer;
• patterning the gate layer, including the hard mask layer, to form a gate structure including edges, while the hard mask layer remains on the gate structure;
• forming a dielectric layer overlying the gate structure and hard mask layer to protect the gate structure including the edges;
• patterning the dielectric layer to form sidewall spacer structures on the gate structure, including the edges, while the hard mask layer remains on the gate structure;
• etching a source region and a drain region adjacent to the gate structure using the dielectric layer and portion of the hard mask layer as a protective layer;
• depositing silicon germanium material into the source region and the drain region to fill the etched source region and the etched drain region to cause 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;
• forming a blanket layer of material having an initial thickness overlying the source region, the drain region, and the gate structure to cover an upper surface of the gate structure, including the hard mask layer, to form a substantially planarized surface region from the blanket layer;
• removing a portion of the initial thickness of the blanket layer to remove the hard mask and expose a portion of the gate structure;
• and
• introducing dopant impurities into the portion of the gate structure using at least an implantation process to dope the gate structure, while maintaining the source region and the gate region free from the dopant impurities.