Alternative methods of fabricating an interconnect structure in which an enhanced diffusion barrier including an in-situ formed metal nitride liner formed between an interconnect dielectric material and an overlying metal diffusion barrier liner are provided. In one embodiment, the method includes forming at least one opening into an interconnect dielectric material. A nitrogen enriched dielectric surface layer is formed within exposed surfaces of the interconnect dielectric material utilizing thermal nitridation. A metal diffusion barrier liner is formed on the nitrogen enriched dielectric surface. During and/or after the formation of the metal diffusion barrier liner, a metal nitride liner forms in-situ in a lower region of the metal diffusion barrier liner. A conductive material is then formed on the metal diffusion barrier liner. The conductive material, the metal diffusion barrier liner and the metal nitride liner that are located outside of the at least one opening are removed to provide a planarized conductive material, a planarized metal diffusion barrier liner and a planarized metal nitride liner, each of which includes an upper surface that is co-planar with the nitrogen enriched dielectric surface layer of the interconnect dielectric material.