The invention relates to an integrated anode and activated reactive gas source (20) for use in a magnetron sputtering device (10) and a magnetron sputtering device incorporating the same. The integrated anode and activated reactive gas source (20) comprises a vessel having an interior conductive surface (22), comprising the anode, and an insulated outer body (26) isolated from the chamber walls (32) of the coating chamber (2). The vessel has a single opening (21) with a circumference smaller that that of the vessel in communication with the coating chamber (2). Sputtering gas and reactive gas are coupled through an input (29) into the vessel and through the single opening (21) into the coating chamber (2). A plasma is ignited by the high density of electrons coming from the cathode (12) and returning to the power supply through the anode (22). A relatively low anode voltage is sufficient to maintain a plasma of activated reactive gas to form stoichiometric dielectric coatings.