Effects of deposited cobalt film thickness on the epitaxial growth of CoSi2 on Si(111) by the solid phase epitaxy regime have been studied using transmission electron microscopy. Thinner films (30 Å) facilitate the growth of epitaxial CoSi2, the formation of smooth silicide-Si interfaces and even the growth of single-crystal CoSi2 at low annealing temperatures, but degrade in thermal stability. Thicker films (300 Å) retard the grain realignment, and yield faceted epitaxial structure after high temperature annealing. Hence, film thicknesses sufficient to benefit from easy epitaxial growth and forming flat silicide-Si interfaces and yet are thermally stable should be used. Accordingly, a facet-free, thermally stable, single-crystal CoSi2 structure has been achieved using 100 Å thick films.