Abstract: Silicon dioxide is pyrolytically deposited by the reaction of silane with oxygen on vertically mounted substrates in an evacuated system. A standard diffusion furnace equipped with a furnace tube which is vacuum tight is used. Injection tubes having multiple injection ports are positioned within the furnace tube to distribute the silane and the oxygen uniformly across a plurality of substrates which are positioned perpendicular to the furnace tube axis in a boat covered with a perforated shroud. The process is particularly useful in providing for the low temperature deposition of uniform layers of silicon dioxide on silicon wafers to be used in the fabrication of semiconductor devices.