In metallization systems of complex semiconductor devices, an intermediate interface layer may be incorporated into the interconnect structures in order to provide superior electromigration performance. To this end, the deposition of the actual fill material may be interrupted at an appropriate stage and the interface layer may be formed, for instance, by deposition, surface treatment and the like, followed by the further deposition of the actual fill metal. In this manner, the grain size issue, in particular at lower portions of the scaled inter-connect features, may be addressed.