UV light-exited ozone has been applied for rapid low-temperature oxidation of silicon in a wafer-transfer type chamber. Oxidation was made in almost 100% ozone atmosphere with KrF excimer laser (248 nm) which enables the effective supply of O (1D) atoms to the processed surface. In this system, SiO2 film with a thickness of more than 3.5 nm is achieved even as low as 200°C. Uniform 2.9 nm film formation over 5-inch wafer with a thickness fluctuation of 0.1 nm was also obtained when KrF laser irradiation area was enlarged by a cylindrical concave lens. Current-voltage measurement has been employed to characterize SiO2 films and it is confirmed that the catastrophic breakdown field strength was 13 MV/cm. Processing pressure dependence of density of O (1D) atoms which contributing to the oxidation was estimated. Experimental result that the thickness of SiO2 film increases by decreasing the processing pressure agrees with our estimated result at the pressure range between 340 Pa and 820 Pa.