An integrated circuit device includes a metal film and a complex capping layer covering a top surface of the metal film. The metal film includes a first metal, and penetrates at least a portion of an insulating film formed over a substrate. The complex capping layer includes a conductive alloy capping layer covering the top surface of the metal film, and an insulating capping layer covering a top surface of the conductive alloy capping layer and a top surface of the insulating film. The conductive alloy capping layer includes a semiconductor element and a second metal different from the first metal. The insulating capping layer includes a third metal.