We have investigated the effect of native oxide on the epitaxial SiGe from deposited amorphous Ge on Si. Instead of epitaxial growth by molecular beam epitaxy or ultrahigh-vacuum chemical vapor deposition, the SiGe layer is formed by this simple process followed by an annealing step. As observed by transmission electron microscopy, the suppression of native oxide plays an important role to achieve epitaxial SiGe. The SiGe quality degrades with increasing native oxide thickness and becomes polycrystalline with a ∼20 Åinterfacial native oxide. On the other hand, single crystalline SiGe can be routinely formed from a HF-vapor treated Si surface.