Single‐crystal CoSi2films have been grown in solid phase epitaxy regime under nonultrahigh vacuum conditions on (111) Si by electron gun deposition of Co thin films followed by rapid thermal annealing in Ar ambient. The single‐crystal films were analyzed by transmission electron microscopy to share the (111) Si surface normal but are rotated 180° about that axis with respect to the substrate. The effect of gas ambient was found to be of critical importance in the growth of single‐crystal CoSi2on (111) Si. The present nonultrahigh vacuum treatments to grow single‐crystal films on silicon shall greatly facilitate the fabrication of novel classes of high‐speed and high‐frequency devices employing buried silicide layers.