Epitaxial ruthenium silicides have been successfully grown on silicon for the first time. Chemical electroless plating of a Ru thin film on silicon with subsequent annealing is a new approach and also the first demonstration of epitaxial growth of these silicides. Transmission electron microscopy was applied to characterize phases of silicides, microstructure, and orientation relationships. Three different epitaxial phases were found and identified to be Ru2Si3, RuSi, and Ru2Si. RuSi and Ru2Si are two new phases discovered in comparison with those previously reported in thin film reactions. Furthermore, Ru2Si3was found to be a stable phase at elevated temperatures since it can be transformed from Ru2Si and RuSi by sufficiently long annealing. Various diffraction patterns were analyzed and orientation relationships were determined. Moire’s fringes of RuSi and interfacial dislocations of Ru2Si3and Ru2Si were found. The average spacings were measured to be from 1000 to 4000 A˚ for Ru2Si3/Si. The composition of the silicides was measured by scanning Auger electron spectroscopy and 2% phosphorus was found.