A diffusion barrier stack is formed by forming a layer comprising a metal over a conductor that includes copper; and forming a first dielectric layer over the layer, wherein the dielectric layer is of a thickness that alone it can not serve as a diffusion barrier layer to the conductor and the first dielectric layer prevents oxidation of the layer. In one embodiment, the diffusion barrier stack includes two layers; the first layer is a conductive layer and the second layer is a dielectric layer. The diffusion barrier stack minimizes electromigration and copper diffusion from the conductor.