A device for doping, deposition or oxidation of semiconductor material at low pressure in a process tube, is provided with a tube closure as well as devices for supplying and discharging process gases and for generating a negative pressure in the process tube. A closure of the process chamber that is gas tight with respect to the process gases and the vacuum tight seal of the end of the tube closure are spatially separated from each other in relation to the atmosphere and are arranged on a same side of the process tube in such a manner that a bottom of a stopper, sealing the process chamber, rests against a sealing rim of the process tube and the tube closure end is sealed vacuum tight by a collar, which is attached to the process tube and against which a door rests sealingly.