A device for treating a web material in a continuous plasma enhanced process includes a vacuum chamber (1) with device (2) for maintaining a constant reduced pressure within the chamber (1) and, arranged within the chamber (1), a rotating drum (3) for supporting and transporting the web (4), a magnetron device facing the web (4) supported and transported by the drum (3) and a gas supply device for supplying a process gas or process gas mixture to the space (10) between the drum and the magnetron device in which space (10) the plasma is sustained. The magnetron device has a plurality of independent magnetron electrodes (6) with rectangular magnetron faces arranged beside each other in parallel. Each magnetron electrode (6) is individually powered with an alternating voltage by its own power supply (7). The drum (3) is electrically grounded, floating or negatively biased.