We report our investigations of the nickel silicide based contact layers prepared for silicon power diodes by electroless nickel plating followed by furnace annealing and subsequent electroless deposition of contact layers. Selected properties of the final structure were studied by the SEM/EDS, micro-Raman spectroscopy and TOP SIMS. The distribution of the species in contacts, quality of interfaces and the role of technological conditions to the formation of the nickel silicide layers were examined in details