The Si/SiO2 interface formed by remote plasma enhanced chemical vapor deposition (RPECVD) at low temperature with SiH4/N2O or SiH4/N2O/Cl-2 was studied and compared with thermal oxidation. The interface of the CVD SiO2 without chlorine addition is rougher than that with chlorine addition. But the surface roughness of CVD SiO2 films increases with chlorine addition. The thermal oxidation induces strong interface strains, and the strains generated by the CVD SiO2 without chlorine addition are stronger and are distributed more nonuniformly than those by the chlorinated SiO2. It is believed that chlorine addition during RPECVD affects the initial stages of deposition, and chlorine is combined with Si dangling bonds existing at the Si/SiO2 interface through the formation of Si-Cl-x bonds. It was also found that with chlorine addition during RPECVD, the strained layer thickness, interface trap density, and suboxide density could be lowered significantly.