A method is provided to form densely spaced metal lines. A first set of metal lines is formed by etching a first metal layer. A thin dielectric layer is conformally deposited on the first metal lines. A second metal is deposited on the thin dielectric layer, filling gaps between the first metal lines. The second metal layer is planarized to form second metal lines interposed between the first metal lines, coexposing the thin dielectric layer and the second metal layer at a substantially planar surface. In some embodiments, planarization continues to remove the thin dielectric covering tops of the first metal lines, coexposing the first metal lines and the second metal lines, separated by the thin dielectric layer, at a substantially planar surface.