Back end of line (BEOL) metallization structures and methods according to aspects of the invention generally include forming an interconnect structure including a recessed via structure in an interlayer dielectric. The recessed via structure is lined with a liner layer and filled with a first metal such as copper, tungsten, aluminum, alloys thereof or mixtures thereof. The recessed portion is filled with a second metal such as tantalum, titanium, tungsten, cobalt, ruthenium, iridium, platinum, nitrides thereof, or mixtures thereof, which in combination with the liner layer provides effective barrier properties for the bulk first metal.