A method for forming a semiconductor structure includes forming a dielectric layer over a substrate. A first non-conductive barrier layer is formed over the dielectric layer. At least one opening is formed through the first non-conductive barrier layer and within the dielectric layer. A second non-conductive barrier layer is formed over the first non-conductive barrier layer and within the opening. At least a portion of the second non-conductive barrier layer is removed, thereby at least partially exposing a top surface of the first non-conductive barrier layer and a bottom surface of the opening, with the second non-conductive barrier layer remaining on sidewalls of the opening. A seed layer and conductive layer is then formed and a single polishing operation removes the seed layer and conductive layer.