Metastable O(D-1) atoms produced in rare gas diluted O-2 plasmas are believed to be the key of high quality SiO2 film formation at low substrate temperatures. The authors diagnosed the behavior of the O(D-1) density in highly rare gas diluted O-2 plasma and applied the increased O(D-1) flux to the formation of thin SiO2 films on Si (100) substrate. O(D-1) flux increases 4.5 times with Kr (97%) dilution of O-2 plasma while it increases 2.8 times for the case of Ar (97%). X-ray photoelectron spectroscopy spectrum showed Si-Si bond in the grown film was decreased by rare gas diluted plasmas. The stoichiometry of the film is improved by Ar and Kr dilution and corresponds to the increase in O(D-1) flux to the surface. Electrical breakdown field measured by atomic force microscopy was 1.5 times higher for Kr/O-2 plasma grown film compared to the pure O-2 case and supports the quality of the film. (C) 2008 American Vacuum Society.