US Patent 9793212 Interconnect structures and methods of forming same

An embodiment semiconductor device includes a first conductive feature in a dielectric layer and a second conductive feature over the dielectric layer and electrically connected to the first conductive feature. The second conductive feature includes a dual damascene structure and further includes a top portion within both a line portion and a via portion of the second conductive feature and a bottom portion in the via portion of the second conductive feature. The bottom portion comprises a different conductive material than the top portion, and a thickness of the bottom portion is at least about twenty percent of a total thickness of the via portion of the second conductive feature.