MnSi epitaxial layers have been grown on (111) and (001)-oriented Si substrates by Mn deposition and reaction with Si in the presence of an Sb flux. Characterization using transmission electron microscopy (TEM) confirmed the formation of high-quality epitaxial layers with smooth interfaces between the MnSi and the Si(111)substrate, when grown under optimal conditions, without the deposition of elemental Sb or Sb-based compounds. MnSi layers are found to be rotated 30 degrees with respect to the Si(111) substrate to reduce the lattice mismatch. Evidence only for the presence of MnSi was found and there was no evidence of any other Mn-Si phases. The additional formation of MnSb is found to depend on the rate of formation of MnSi, which is primarily governed by the Mn flux rate and the growth temperature. By way of comparison, polycrystalline mixed phase Mn-silicide layers were formed by direct deposition of Mn and reaction with Si(111) at elevated temperatures in the absence of an Sb flux.