The concept of atomically controlled processing for group IV semiconductors is shown based on atomic-order surface reaction control in Si-based CVD epitaxial growth. Si or Si1-xGex epitaxial growth on N, P or C atomic layer formed on Si(100) or Si1-xGex (100) surface, is achieved at temperatures below 500 °C. In the Si 0.5Ge0.5 epitaxial layer, a N doping dose of 6x10 14 cm-2 is confined within an about 1.5 nm thick region and the confined N atoms in Si1-xGex preferentially form Si-N bonds. In Si cap layer growth on the P atomic layer formed on Si 1-xGex(100) with the P atom amount below about 4x10 14 cm-2 using Si2H6 instead of SiH4, the incorporated P atoms are almost confined within the 1 nm region around the heterointerface. Heavy C atomic-layer doping suppresses strain relaxation as well as intermixing between Si and Ge at the nm-order thick Si1-xGex/Si heterointerface. These results open the way to atomically controlled processing for ULSIs.