SIMOX (separation by implanted oxygen) wafers were implanted with high doses of cobalt and annealed at high temperatures in order to study the formation of buried single-crystal CoSi 2 layers in this material. For this study SIMOX wafers of (100) oriented silicon were implanted at 100-200 keV with doses of 1.2-2.0 x 1017 Co + cm-2, and annealed in a rapid thermal processor or tube furnace. As-implanted and annealed samples were analyzed by Rutherford backscattering with channeling spectroscopy (RBS), cross-sectional transmission electron microscopy (XTEM), secondary ion mass spectroscopy, and the van der Pauw technique. The best buried CoSi 2 layers were obtained at an implantation energy of 100 keV and by subsequent rapid thermal annealing. RBS minimum yields of approximately 6% were obtained for the buried layer, which is the same as that reported for bulk (100) silicon. The measured resistivity of 15 kt ~ cm and XTEM confirmed the continuity of the layer. Buried CoSi 2 layers were successfully produced up to an implantation energy of 180 keV. However, as the energy was increased the quality of the CoSi 2 layer degraded, with minimum yields increasing to 24% at 180 keV, and with a corresponding degradation in the minimum yields in the top silicon layer. At 200 keV a buried epitaxial layer was not produced. The degradation of crystal quality with ion implantation energy and the failure to produce a buried layer at 200 keV are discussed.