Abstract: A sputtering apparatus and method for high rate deposition of electrically insulating and semiconducting coatings with substantially uniform stoichiometry. At least one set of vertically mounted, dual and triple rotatable cylindrical (or planar) magnetrons with associated vacuum pumps, form semi-isolated sputtering modules. The sputtering modules can be independently controlled for the sequential deposition of layers of similar or different materials. Constant voltage operation of AC power with an optional reactive gas flow feedback loop maintains constant coating stoichiometry during small changes in pumping speed caused by substrate motion. The coating method is extremely stable over long periods (days) of operation, with the film stoichiometry being selectable by the voltage control point.