A chemical vapor deposition apparatus includes a subatmospheric substrate transfer chamber. A subatmospheric deposition chamber is defined at least in part by a chamber sidewall. A passageway in the chamber sidewall extends from the transfer chamber to the deposition chamber. Semiconductor substrates pass into and out of the deposition chamber through the passageway for deposition processing. A mechanical gate is included within at least one of the deposition chamber and the sidewall passageway, and is configured to open and close at least a portion of the passageway to the chamber. A chamber liner apparatus of a chemical vapor deposition apparatus forms a deposition subchamber within the chamber. At least a portion of the chamber liner apparatus is selectively movable to fully expose and to fully cover the passageway to the chamber.