Silicon oxide films were deposited at near room temperature by a remote-type radio frequency plasma-enhanced chemical vapor deposition using a mixture of tetramethoxysilane and oxygen as source gas. The temperature of the reactor wall was controlled from 25 to 150 degreesC. Carbon impurities which existed as Si-CH3 in the deposited films were reduced markedly when the substrate temperature was kept higher than the wall temperature during deposition. The optimum substrate temperature was 50 degreesC to obtain carbon-free silicon oxide films at a wall temperature of 30 degreesC. X-Ray photoelectron spectroscopic analyses of the films proved that carbon impurities existed only on the film surfaces.