Method for forming metal replacement gate of high performance

A method of fabricating a gate structure of an integrated circuit, comprising:

• forming a metal-containing gate in an opening within a dielectric region formerly occupied by a sacrificial gate, said metal-containing gate including:
• a first layer consisting essentially of tungsten deposited from a W(CO)6 precursor, said first layer contacting a gate dielectric, the gate dielectric contacting a transistor channel region formed in a semiconductor region of a substrate;
• a diffusion barrier layer overlying said first layer;
• and
• a second layer overlying said diffusion barrier layer, said second layer consisting essentially of tungsten deposited from a WF6 precursor, at least one of said first layer and said second layer including an impurity concentration to adjust said metal gate to a desired workfunction.

A method of making a metal gate structure on a substrate comprising:

• forming an etch stop layer on a semiconductor region of a substrate;
• forming a sacrificial gate on said etch stop layer;
• providing a pair of dielectric spacers on sidewalls of said sacrificial gate;
• forming a dielectric layer on said substrate having a top surface generally planar to a top of said sacrificial gate;
• removing said sacrificial gate to form an opening between said spacers;
• removing said etch stop layer from under said opening;
• forming a gate dielectric on said semiconductor region under said opening;
• depositing from a W(CO)6 a first layer consisting essentially of tungsten in said opening, said first layer contacting said gate dielectric and sidewalls of said spacers;
• forming a diffusion barrier layer on said first layer in said opening;
• and
• depositing a from a W(CO)6 a second layer consisting essentially of tungsten in said opening, said second layer contacting said diffusion barrier layer.