Metal cap layer with enhanced etch resistivity for copper-based metal regions in semiconductor devices

During the fabrication of sophisticated metallization systems of semiconductor devices, material deterioration of conductive cap layers may be significantly reduced by providing a noble metal on exposed surface areas after the patterning of the corresponding via openings. In one embodiment, a semiconductor device is provided that includes a metallization system formed above a substrate. The metallization system includes a metal line formed in a dielectric layer and having a top surface. The metallization system also includes a conductive cap layer formed on the top surface. A via extends through the conductive cap layer and connects to the top surface of the metal line. A conductive barrier layer is formed on sidewalls of the via. An interface layer is formed of a noble metal between the conductive cap layer and the conductive barrier layer and between the top surface of the metal line and the conductive barrier layer.