The atomically smooth SrTiO3 (100) with steps one unit cell in height was obtained by treating the crystal surface with a pH-controlled NH4F-HF solution. The homoepitaxy of SrTiO3 film on the crystal surface proceeds in a perfect layer-by-layer mode as verified by reflection high-energy electron diffraction and atomic force microscopy. ion scattering spectroscopy revealed that the TiO2 atomic plane terminated the as-treated clean surface and that the terminating atomic layer could be tuned to the SrO atomic plane by homoepitaxial growth. This technology provides a well-defined substrate surface for atomically regulated epitaxial growth of such perovskite oxide films as YBa2Cu3O7-delta.