The effects of oxygen mixing into argon sputtering gas on the properties of silicon oxide films are presented. The silicon oxide films were deposited from an target at low temperature (200°C). The oxygen mixing confirms that the film properties of sputter‐deposited films can be considerably improved to the same level as those of thermal oxide film. Moreover, the oxygen mixing improves the electrical characteristics of sputter‐deposited films resulting in a high resistivity of >1015 Ω · cm and a high breakdown field of >7.5 MV/cm. In addition, measurements of MOS capacitors featuring sputter‐deposited films as gate oxide films indicate that an excellent surface‐state density can be achieved. Oxygen‐argon sputter deposition is thus proved very useful for low temperature silicon dioxide film formation in MOSFET fabrication.