Work Function Material Protection in Wide Replacement Gate Electrodes

A dielectric material layer is introduced as an intermediary between the work function metal layer and the etching process. This dielectric layer is deposited over the work function metal, patterned to expose only the edges, and serves as a protective mask during selective recessing. The dielectric intermediary prevents direct etching of the work function metal center portion, maintaining its uniform thickness while allowing the gate electrode width to be greater than the metal thickness.

The work function metal layer is configured with different thicknesses in different regions: thinner at the edges where it contacts the gate dielectric, and thicker in the center portion where it is protected by the dielectric mask. This local quality variation allows the metal to maintain contact coverage across wide gate cavities while minimizing overall resistance, as the current path primarily utilizes the conductive work function metal without requiring excessive thickness.

The dielectric material layer is deposited and patterned in advance, before the recessing of the work function metal layer. This preliminary action creates a protective mask that prevents the work function metal from being completely removed during subsequent etching. The dielectric layer is formed, planarized, and recessed to expose only the work function metal edges, establishing a protective structure that maintains metal thickness uniformity throughout the wide gate cavity.