Grazing angle Rutherford Backscattering Spectrometry/Channeling(RBS/C) with an improved depth resolution (2-3nm) in combination with X-ray photoelectron Spectroscopy (XPS) was used to investigate the thin oxide of Si(1-x)Ge(x) (x=0, 0.2 and 0.3) films oxidized at elevated temperatures in a dry chlorinated ambient atmosphere (O2/Cl). Experimental results showed that after oxidation, only SiO2 was formed while Ge was completely rejected from the oxide to form Ge-rich layers. The effect of the oxidation enhancement of the SiGe alloy with an increase in the Ge content was also found in this study. The strain of the unoxidized SiGe layer underneath the oxide layer characterized by channeling angular scans indicates that these rejected Ge atoms during oxidation have less influence on the integrity of the SiGe layer due to diffusion of the Ge atoms.