Integrated circuit and method for fabricating the same having a replacement gate structure

A method for fabricating an integrated circuit, comprising:

• providing a semiconductor substrate having first and second dummy gate structures formed thereon, each of the first and second dummy gate structures comprising at least a dummy gate electrode formed of a dummy gate material and sidewall spacers formed on vertical sidewalls of the dummy gate electrodes;
• removing, by etching, an entirety of the dummy gate electrodes of both the first and second dummy gate structures so as to expose a silicon material at the semiconductor substrate and so as to expose vertical walls of the sidewall spacers, thereby forming a first trench in place of the dummy gate electrode of the first dummy gate structure and a second trench in place of the dummy gate electrode of the second dummy gate structure, each of the first and second trenches being defined by the sidewall spacers and the silicon material at the semiconductor substrate;
• forming, by conformal deposition, a high-k dielectric material within both the first and second trenches including over an entirety of the exposed silicon material and along an entirety of the exposed vertical walls of the sidewall spacers;
• forming a first layer comprising a first workfunction material in the first trench, but not in the second trench, so as to fill an entirety of the first trench, but none of the second trench, wherein the first workfunction material is of a first conductivity-determining type;
• forming a second layer comprising a second workfunction material in the second trench, but not in the first trench, wherein the second layer only partially fills the second trench leaving a portion of the second trench unfilled, but does not fill any of the first trench, and wherein the second workfunction material is of a second conductivity-determining type that is different than the first conductivity-determining type;
• depositing a low-resistance fill material onto the integrated circuit so as to fill the second trench with the low-resistance fill material, wherein the first trench remains entirely filled by the first layer and as such no low-resistance fill material enters the first trench;
• etching the low resistance fill material, the first layer, and the second layer in areas between at least a portion of the sidewall spacers so as to re-expose a portion of both the first and second trenches, wherein the re-exposed portion of the first trench is defined by a remaining portion of the first layer that extends to a first height above the semiconductor substrate and by the high-k material deposited along the sidewalls, and wherein the re-exposed portion of the second trench is defined by a remaining portion of the second layer and the low-resistance fill material each of which extending to the first height above the semiconductor substrate, the first height being lower than a height of the sidewall spacers, and by the high-k material deposited along the sidewalls, while leaving the remaining portion of each of the first layer, the second layer, and the low-resistance fill material in place, and wherein the re-exposed portion of the first and second trenches comprises a void space located between at least a portion of the sidewall spacers of each respective re-exposed trench portion, and wherein the void space extends from the first height to the height of the sidewall spacers;
• forming, by conformal deposition, a barrier material layer within the first and second re-exposed trench portions, wherein the barrier material layer does not completely fill either the first or the second re-exposed trench portion;
• and
• depositing a gate fill material into each re-exposed trench portion so as to completely fill an entirety of both the first and the second re-exposed trench portions.