A general mathematical model for the description of heat transfer and mass transport processes in a hotwall multiple-wafer horizontal tube LPCVD reactor is developed. Investigations on the influence of the geometric characteristics of the reactor system on the thickness uniformity of the layers and on the economically expedient performance of the processes are carried out by the model. In this way, information about the optimum geometry of the reactor is obtained. Technical modifications of the conventional LPCVD systems are analyzed which allow the obtainment of uniform layers under conditions of mass production without applying temperature difference along the reaction zone. A model of injection-fed reactors is built that helps make conclusions about the optimum design of the injectors when they are used in a regime of maintaining constant concentration in the system.