Abstract: An apparatus for performing vapor deposition processes on a substrate includes essential housing having a centrally located reaction chamber, with the housing having a pair of opposed openings in opposed sides thereof. Cover means are removably secured to the housing for closing the opening and they define coolant chambers therein. Reaction gases are supplied and exhausted from the reaction chamber through a ducting system, and the housing includes at least one additional coolant chamber therein about periphery of the reaction chamber between the cover plates. Coolant is supplied to and exhausted from the coolant chambers in order to cool the reaction chamber, and support means are provided in the reaction chamber supporting a substrate thereon upon which vapor deposition is to occur. Heat is supplied in the reaction chamber on the side of the support means opposite the substrate to heat the substrate.