A postannealing technique was developed in order to improve the quality of SiO2films formed by a parallel‐plate remote plasma chemical vapor deposition. The wave number of the antisymmetric stretching mode of Si–O–Si bonding in the SiO2film increased from 1058 to 1069 cm−1by an annealing in H2O vapor at 270 °C. It was estimated that averaged bonding angle of Si–O–Si was widened from 137.8° to 141.0°. The annealing in the H2O vapor ambient at 270 °C for 30 min efficiently reduced the interface trap density to 2.0×1010cm−2 eV−1and the effective oxide charges density from 7×1011to 5×109cm−2for a metal‐oxide‐semiconductor (MOS) diode using the SiO2film. ©1995 American Institute of Physics.