Microwave remote plasma oxidation were used to study the oxidation of Si and SiGe samples at a lower temperature. C–V measurements were performed to investigate the trap density, and the corresponding bonding structures of thin oxide were revealed by FTIR analysis. SIMS depth profiles were used to reveal the extent of the Ge segregation in SiGe samples. The system can grow ultra thin SiO2 with lower effective trap density. And Ge segregation can be largely suppressed by atomic oxygen oxidation at a lower temperature.