Integrated circuits having improved metal gate structures and methods for fabricating same

A method for fabricating an integrated circuit, the method comprising:

• forming a trench in an interlayer dielectric material on a semiconductor surface;
• depositing an N-type work function metal layer over the interlayer dielectric material adjacent the trench and partially filling the trench with the N-type work function metal layer to define an inner cavity;
• depositing tungsten nitride over the N-type work function metal layer adjacent the trench and partially filling the inner cavity to define a central void;
• depositing tungsten over the tungsten nitride adjacent the trench and filling the central void to form a metal gate structure;
• planarizing the N-type work function metal, the tungsten nitride, and the tungsten to a surface aligned with the interlayer dielectric material;
• and
• recessing the N-type work function metal, the tungsten nitride, and the tungsten during a single recessing process to form a recess over the N-type work function metal, the tungsten nitride, and the tungsten in the trench.

A method for fabricating an integrated circuit, the method comprising:

• forming a PFET trench in a PFET region and an NFET trench in an NFET region of an interlayer dielectric material on a semiconductor surface, wherein a region of interlayer dielectric material separates the PFET trench from the NFET trench;
• partially filling the NFET trench with an N-type work function metal layer to define an inner cavity;
• partially filling the PFET trench and the inner cavity in the NFET trench with a P-type work function metal layer to define a central void in each trench;
• filling the central voids with a metal fill;
• and
• performing a single recessing process to recess portions of the metal fill, the N-type work function metal layer, and the P-type work function metal layer in the NFET trench and portions of the metal fill and the P-type work function metal layer in the PFET trench to form a recess in each trench.