Silicon dioxide thin films were deposited on p-type Si (100) substrates by atomic layer deposition (ALD) method using alternating exposures of SiH 2 Cl 2 and O 3 at 300 ? C . O 3 was generated by corona discharge inside the delivery line of O 2 . The oxide film was deposited mainly from O 3 not from O 2 , because the deposited film was not observed without corona discharge under the same process conditions. The growth rate of the deposited films increased linearly with increasing the exposures of SiH 2 Cl 2 and O 3 simultaneously, and was saturated at approximately 0.35 nm/cycle with the reactant exposures over 3.6 {\times}10 9 /L. At a fixed SiH 2 Cl 2 exposure of 1.2 {\times}10 9 L, growth rate increased with O 3 exposure and was saturated at approximately 0.28 nm/cycle with O 3 exposures over 2.4 {\times}10 9 L. The composition of the deposited film also varied with the exposure of O 3 . The [O]/[Si] ratio gradually increased up to 2 with increasing the exposure of O 3 . Finally, the characteristics of ALD films were compared with those of the silicon oxide films deposited by conventional chemical vapor deposition (CVD) methods. The silicon oxide film prepared by ALD at 300 ? C showed better stoichiometry and wet etch rate than those of the silicon oxide films deposited by low-pressure CVD (LPCVD) and atmospheric-pressure CVD (APCVD) at the deposition temperatures ranging from 400 to 800 ? C .