The present disclosure is directed to an apparatus for depositing a layer of a material on a wafer. The apparatus includes a deposition chamber having an upper dome, a lower dome and a side wall between the upper and lower domes. A susceptor plate is in and extends across the deposition chamber to divide the deposition chamber into an upper portion above the susceptor plate and a lower portion below the susceptor plate. A gas inlet manifold is in the side wall. The manifold has three inlet ports. One of the ports is connected by passages which open into the lower portion of the deposition chamber. The other two ports are connected by passages which open into the upper portion of the deposition chamber. A gas supply system is connected to the inlet ports so as to provide the same gases into the lower portion of the deposition chamber as well as into the upper portion of the deposition chamber. This allows the back surface of the susceptor plate to be coated with a layer of the same material as to be coated on the wafer prior to coating the layer on the wafer.