Disclosed is a method which includes forming a copper interconnect within a trench or via in a substrate. Forming the copper interconnect includes forming a ruthenium-containing seed layer on a wall of the trench or via; forming a cobalt sacrificial layer on the ruthenium-containing layer before the ruthenium-containing seed layer being exposed to an environment that is oxidizing with respect to the seed layer; and contacting the cobalt sacrificial layer with a copper plating solution, the copper plating solution dissolving the cobalt sacrificial layer and plating out copper on the unoxidized ruthenium-containing seed layer. Alternatively, the ruthenium-containing seed layer may be replaced with platinum, tungsten nitride, titanium nitride or titanium or iridium. Further alternatively, the cobalt sacrificial layer may be replaced by tin, cadmium, copper or manganese.