Method of forming a single metal that performs N work function and P work function in a high-k/metal gate process

A method of fabricating a semiconductor device comprising:

• forming an interfacial layer over a semiconductor substrate;
• forming a high-k dielectric layer over the interfacial layer;
• forming a metal layer over the high-k dielectric layer, the metal layer having a first work function;
• treating a portion of the metal layer with Al such that a work function of the portion of the metal layer changes from the first work function to a second work function;
• and
• forming a first metal gate from an untreated portion of the metal layer having the first work function and forming a second metal gate from the treated portion of the metal layer having the second work function, wherein the untreated portion is not treated with a plasma or implantation process.

A method of fabricating a semiconductor device comprising:

• forming an interfacial layer over a semiconductor substrate;
• forming a gate dielectric layer over the interfacial laver;
• forming a metal layer over the gate dielectric layer, the metal layer having a first work function;
• performing an Al implantation process on one portion of the metal layer such that a work function of the portion of the metal layer changes from the first work function to a second work function, wherein the Al implantation process comprises an implant tilt angle of about 7 degrees;
• and
• forming a first metal gate from an untreated portion of the metal layer having the first work function and forming a second metal gate from the treated portion of the metal layer having the second work function, wherein the untreated portion is not treated with a plasma or implantation process.