A deposition apparatus for processing substrates includes a vacuum chamber including a processing zone in which a substrate may be processed. First and second gas sources are in fluid communication with the vacuum chamber. The first gas source is operable to supply a first gas into the vacuum chamber and the second gas source is operable to supply a second gas into the vacuum chamber. A showerhead assembly includes a face plate and back plate. The back plate includes a first gas inlet in fluid communication with the first gas source and a second gas inlet in fluid communication with the second gas source. The face plate includes a lower wall and an outer wall extending vertically upwardly from an outer periphery of the lower wall. The outer wall is sealed to an outer periphery of the back plate such that an inner plenum and an edge plenum are formed between the face plate and the back plate. The face plate includes a first gas permeable region in fluid communication with the first gas inlet via the inner plenum such that the first gas may be supplied therethrough during processing and a second gas permeable region in fluid communication with the second gas inlet via the edge plenum such that a second gas may be supplied therethrough during processing. A substrate pedestal assembly is configured to support a substrate on an upper surface thereof when a substrate is processed in the deposition apparatus.