A novel film deposition method called radical shower chemical vapor deposition (RS-CVD) has been developed for high-quality gate-oxide (SiO 2 ) film formation on low-temperature poly-Si TFT-LCD. RS-CVD is characterised by a plasma damage-free deposition on a large area substrate at a low temperature, although discharge is used to generate the activated species of oxygen radicals. In film deposition, by using a reaction of SiH 4 with oxygen radicals, it is possible to grow SiO 2 films under low substrate temperature at low deposition pressure. Dependencies of film properties on deposition parameters are investigated to optimize the RS-CVD process. The parameter dependencies are interpreted with consideration of the gas phase reaction mechanisms, which account for the observable consequences of Si-OH bonds quantity incorporated in the films. Throughout this study, it is concluded that it is necessary for the film quality to reduce the contamination of intermediate species containing Si-OH bonds in the films and to control the excess reaction in the gas phase. Besides, the increase in the oxygen radical quantity is effective for the improvement of film properties.