Gate Structure of a Semiconductor Device and Method of Forming Same

A semiconductor device comprising:

• a substrate, the substrate having a first region and a second region;
• and
• a gate structure over the substrate, wherein a first portion of the gate structure is above the first region and a second portion of the gate structure is above the second region, and wherein the gate structure comprises:
• a first gate dielectric layer over the first region;
• a second gate dielectric layer over the second region;
• a first p-type work function layer over the first gate dielectric layer, the first p-type work function layer having a sidewall above an interface between the first region and the second region;
• a second p-type work function layer over the first p-type work function layer and the second gate dielectric layer, wherein the second p-type work function layer has a sidewall above the interface between the first region and the second region;
• a barrier layer in physical contact with the sidewall of the second p-type work function layer, wherein the barrier layer extends along the sidewall of the second p-type work function layer not higher than to a top surface of the second p-type work function layer;
• an n-type work function layer over the second p-type work function layer, wherein the n-type work function layer is in physical contact with a top surface and a sidewall of the barrier layer;
• a first conductive layer over a first portion of the n-type work function layer above the first region;
• and
• a second conductive layer over a second portion of the n-type work function layer above the second region.

A method comprising:

• forming a sacrificial gate over a substrate, the substrate having a first region and a second region, the sacrificial gate extending across an interface between the first region and the second region;
• removing the sacrificial gate to form an opening;
• forming a first gate dielectric layer over the first region in the opening;
• forming a second gate dielectric layer over the second region in the opening;
• forming a first work function layer over the first gate dielectric layer in the opening;
• forming a second work function layer over the first work function layer and the second gate dielectric layer in the opening;
• depositing a dielectric layer over the second work function layer in the opening, wherein the dielectric layer comprises a first material;
• patterning the dielectric layer to form a barrier layer on a sidewall of the second work function layer;
• and
• forming a third work function layer over the second work function layer and the barrier layer.