An integrated circuit includes: a front end of line (FEOL) circuit including a transistor; and a back end of line circuit above the FEOL circuit and including insulator material having an interconnect feature therein. The interconnect feature includes: a core including copper; a first layer between the insulator material and the core, the first layer being distinct from the core; a second layer between the first layer and the core, the second layer being distinct from the first layer and the core, the second layer including a first metal and a second metal different from the first metal; and a capping member on the core and the second layer, the capping member including the second metal. In an embodiment, the first metal and the second metal are part of a solid solution in the second layer. In an embodiment, the first metal is ruthenium and the second metal is cobalt.