A p-type device grade silicon wafer was implanted by 1 MeV Ru+ ions to a dose of 5.67 x 10(16) cm(-2). The microstructures of the as-implanted and annealed samples were studied mainly by analytical transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that the implantation resulted in a well-defined surface layer of about 910 nm in thickness. The layer was composed of ultra-fine Ru2Si3 crystallites in an amorphous matrix. After annealing, the inner part of the layer recovered completely to single crystal Si with nano-scaled Ru2Si3 embedded in it. A similar to 660 nm thick polycrystalline region consisting of Si and Ru2Si3 grains was formed at the surface.