Apparatus for coating a substrate with a material in a chamber subject, during use, to substantial evacuation, which includes a coating station within the chamber for coating a substrate by sputtering and/or by evaporation; at least one treating station disposed in serial with the coating station and equipped with a plasma treater incorporating a plasma generator in sufficient proximity to the substrate to treat the substrate; a magnetic device for generating a magnetic field; at least one cylindrical electrode surrounding the magnetic device, the plasma treater incorporates a device for rotating the electrode about its longitudinal axis.