Abstract: A transfer chamber is provided between MOCVD reaction chamber and load lock chamber, connected to each chamber through an opening for each, for preventing the reaction chamber from the invasion of foreign gases, which may oxydize metals of MOCVD. The load lock chamber can be evacuated or filled with an inert gas, and has a door to the outside for bringing semiconductor wafers in or out. The transfer chamber is provided with a gas inlet and a gas outlet, through each of them an inert gas is always fed and drained for circulation, and also provided with a transfer mechanism therein for transferring wafers between the load lock chamber and the reaction chamber. Wafers are placed on a susceptor connected to the lid, which is driven by the transfer mechanism. A liner tube for protecting the inner surface of the reaction chamber from undesirable contamination caused by MOCVD reaction may be provided detachably attached to the lid to enclose the wafer.