For the purpose of quantum heterointegration of group IV semiconductors, atomically controlled plasma processing by utilizing an electron-cyclotron- resonance (ECR) plasma enhanced chemical vapor deposition (CVD) at low temperature has been developed to achieve atomic-layer doping and heterostructure formation with nanometer-order thickness control as well as smooth and abrupt interfaces. In this paper, recent typical achievements in the plasma processing are reviewed: (1) By N and B atomic-layer formation and Si epitaxial growth on Si(100), heavy atomic-layer doping was demonstrated. Most of the incorporated N or B atoms can be confined in an about 2 nm-thick region. (2) highly-strained and relaxed Ge films on Si(100) with atomic-order flatness can be epitaxially grown. (3) Using a 84% relaxed Ge buffer layer formed on Si(100), formation of a highly strained Si film with nanometer-order thickness was achieved.