A controlled temperature deposition device comprising an inner reaction chamber having gas distribution means for introducing gas into inner chamber and removing gas therefrom and a vacuum chamber means surrounding the inner deposition chamber and spaced from the walls thereof for maintaining a medium vacuum therein. Associated with the deposition device is a substrate loading and unloading fork which transfers substrates such as wafer boats from outside the device to a position in the inner deposition chamber and removes them from the inner deposition chamber following deposition.