The modification of silicon surface due to reactive ion etching (RIE) using a CHF3/C2F6 plasma has been characterized using X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectroscopy (RBS), and high resolution transmission electron microscopy (HRTEM). A flat and uniform residue layer of about 40 angstrom in thickness has been observed in cross-sectional HRTEM work. The interface is sharply defined and smooth. Neither point defect cluster nor distinct planar defect has been found in substrate silicon lattice image. This is also confirmed by comparison scaled and energy shifted silicon surface peak of a control sample with the reactive ion etched sample using ion channeling RBS. NF3, Cl2, and SF6 plasma treatments have been carried out to remove the residue layer. Among them, NF3 treatment has been revealed to be the most effective. With 10 seconds exposure to NF3 plasma, fluorocarbon residue film decomposes, and the remaining fluorine mostly binds to silicon; the fluorine completely disappears after the subsequent wet cleaning.