Apparatus for diffusion treatment of workpieces

In an apparatus for diffusion treatment of workpieces, comprising an outer chamber, wherein at least one reaction region having means for evacuation means is arranged for supplying gas and means for heating the first reaction region within the outer chamber, it is proposed that the means for gas supply is extensively formed and at a small distance from and parallel to the substrate plane, so that the reaction area is limited during operation of the device on one side by the means for gas supply and on the other side by a workpiece to be treated.