Hydrogen gas plays an important role in the epitaxial growth process, acting as both a high temperature precleaning ambient and the carrier gas during epitaxial growth. The effect of hydrogen on the morphology and microroughness of Si(100) and Si(111) surfaces was investigated using atomic force microscopy under an atmospheric air ambient. The Si(100) surface after H2 annealing showed a periodic terrace and step structure reflecting the double-domain (2 x 1 + 1 x 2) reconstructed structure. This structure was maintained even after subsequent HCl vapor etching and epitaxial layer deposition in the Si epitaxial process.