Metal gate structure of a CMOS semiconductor device and method of forming the same

A method of fabricating a CMOS semiconductor device, comprising:

• forming a gate dielectric layer over a substrate, the substrate comprising an isolation region surrounding a P-active region and an N-active region;
• forming a dummy gate electrode layer over the gate dielectric layer;
• patterning the dummy gate electrode layer to form a first dummy strip over the P-active region and isolation region and a second dummy strip over the N-active region;
• removing a first portion of the first dummy strip to form a first opening exposing at least a portion of the P-active region;
• filling the first opening with a first material;
• removing a second portion of the first dummy strip to form a second opening abutting the first material, the second opening exposing at least a portion of the isolation region with the first material abutting the second opening comprising a sidewall substantially aligned with a sidewall of the isolation region;
• removing the second dummy strip to form a third opening;
• and
• filling the second opening and the third opening with a second material,
• the second material being a first metal composition, and the first material being a second metal composition different from the first metal composition.

A method of fabricating a semiconductor device, comprising:

• forming a gate dielectric layer over a substrate, the substrate comprising an isolation region surrounding a P-active region;
• forming a dummy gate electrode layer over the gate dielectric layer;
• patterning the dummy gate electrode layer to form a dummy strip over the P-active region and isolation region;
• removing a first portion of the dummy strip to form a first opening exposing at least a portion of the P-active region;
• filling the first opening with a P-work-function metal;
• removing a second portion of the first dummy strip to form a second opening abutting the P-work-function metal, the second opening exposing at least a portion of the isolation region with the first material abutting the second opening comprising a sidewall substantially aligned with a sidewall of the isolation region;
• and
• filling the second opening with an N-work-function metal.