Abstract: A gas supply system for a gas phase deposition reaction chamber, in particular a CVD gas phase deposition reaction chamber or a PECVD gas phase deposition reaction chamber, comprises a gas supply device which has at least one heating element for heating a deposition medium and transferring the deposition medium into the gaseous phase. Furthermore, the gas supply system comprises a gas feeding device for transporting the gaseous deposition medium from the gas supply device to the gas phase deposition reaction chamber, wherein the gas feeding device comprises a sealing element at the transition to the gas phase deposition reaction chamber. As a result, it is possible to provide a gas supply system for a gas phase deposition reaction chamber allowing a homogeneous feeding of even deposition media which are not present in gaseous form at room temperature into the reaction chamber.