Abstract: A device for treating a surface of a substrate (9) comprises includes a treatment chamber for receiving the substrate therein, and is provided with at least one plasma source for generating a plasma which is connected to the treatment chamber. The plasma source is provided with an inlet means (11) for admitting at least one reactant into a flow path of the plasma. The plasma source (13) comprises includes at least one cathode and at least one anode between which a system of cascade plates is received. The cascade plates are each provided with a number of passage openings to provide a number of separate flow paths for the plasma. Situated preceding the first cascade plate of the system there is a common plasma space which is in open communication with the passage openings in the cascade plates of the system.