Abstract: A CVD reactor includes separate reaction and pressure chambers, where the reaction chamber is contained within and isolates process or reactant gases from the pressure chamber. The reactor also includes a gas injection system which pre-heats and injects diffused process gas(es) into the reaction chamber in a somewhat vertical direction through a bottom surface of the reaction chamber. The gas injection system injects hydrogen or other appropriate gas in a vertical direction through the bottom surface of the reaction chamber. The flow of hydrogen or other appropriate gas is intermediate the flow of the process gas(es) and a surface of the reaction chamber, thereby re-directing the process gas flow parallel to the top surface of a wafer therein. In this manner, the reaction chamber does not require a long entry length for the process gas(es). This flow of hydrogen or other suitable gas also minimizes undesirable deposition on the surface of the reaction chamber.