One of the main requirements for Si-based ultrasmall device is atomic-order control of process technology. Here, we show the concept of atomically controlled processing for group IV semiconductors based on atomic-order surface reaction control in Si-based CVD epitaxial growth. On the atomic-order surface nitridation of Si1-xGex it is suggested that nitridation of Si atoms proceeds by transfer of N atoms from Ge atoms at the surface by heat-treatment. The B atomic-layer doping result suggests that atomic-order Si capping on the B atomic layer already-formed on (100) surface at low temperatures such as 180-300 °C improves the electrical activity even with the subsequent Si capping at 500 °C. Additionally, it is confirmed that the band engineering for group IV semiconductors becomes possible by the strain control of the Si1-xGex/Si heterostructure due to striped patterning. These results demonstrate the capability of the atomically controlled CVD processing approach for future Si-based devices.