A method of forming a doped TaN Cu barrier adjacent to a Ru layer of a Cu interconnect structure and the resulting device are provided. Embodiments include forming a cavity in a SiO-based ILD; conformally forming a doped TaN layer in the cavity and over the ILD; conformally forming a Ru layer on the doped TaN layer; depositing Cu over the Ru layer and filling the cavity; planarizing the Cu, Ru layer, and doped TaN layer down to an upper surface of the ILD; forming a dielectric cap over the Cu, Ru layer, and doped TaN layer; and filling spaces formed between the dielectric cap and the doped TaN layer.