a chemical vapor deposition reactor comprises a deposition zone , a substrate carrier and a liner assembly . the deposition zone is constructed so as to have a positive pressure reactant gases fixed showerhead introducing reactant gas supporting thin film cvd deposition . the substrate carrier movably supports a substrate and the liner assembly within the deposition zone and is heated so as to be subjected to a cvd process . the liner assembly partly encloses selected portions of the deposition zone , particularly portions of the substrate carrier and thereby enclose a hot zone surrounding a substrate to be processed so as to retain heat in that zone but allows gas flow radially outwardly toward walls of a surrounding cold - wall reactor with exhaust ports surrounding the deposition zone that exhaust spent reactant gases . the liner assembly is a sink for solid reaction byproducts while gaseous reaction byproducts are pumped out at the exhaust ports . the liner assembly is linearly movable away from the fixed showerhead .