A new, laminar flow type photochemical vapor deposition method has been applied to prepare a-Si:H films. The main feature of this method is introduction of Ar gas as a flow down gas through the lower part of the quartz window into the reaction chamber to keep the window highly transparent. The high deposition rate (150 angstrom/min) of the a-Si:H film has been stably maintained by optimizing the flow rate for each gas into the chamber. Utilizing this new method, we have been able to realize high quality films with low impurity content, high resistivity (> 10(11) OMEGA-cm), low dangling bond density (5 x 10(15) cm-3), etc.