A structure and method for replacement metal gate technology is provided for use in conjunction with semiconductor fins or other devices. An opening is formed in a dielectric by removing a sacrificial gate material such as polysilicon. The surfaces of the semiconductor fin within which a transistor channel is formed, are exposed in the opening. A replacement metal gate is formed by forming a diffusion barrier layer within the opening and over a gate dielectric material, the diffusion barrier layer formation advantageously followed by an in-situ plasma treatment operation. The treatment operation utilizes at least one of argon and hydrogen and cures surface defects in the diffusion barrier layer enabling the diffusion barrier layer to be formed to a lesser thickness. The treatment operation decreases resistivity, densifies and alters the atomic ratio of the diffusion barrier layer, and is followed by metal deposition.