A showerhead that injects two process gases into the processing chamber via separate sets of holes. The showerhead is constructed of upper plate and lower plate. Upper plate has a first set of holes. The lower plate has two sets of holes: one set is aligned with the holes in the upper plate, while the second set has no corresponding holes in the upper plate. Both sets of holes in the lower plate are made to have two different diameters: a larger diameter extending from the top surface of the lower plate, while a smaller diameter extends from the bottom surface and meets with the larger diameter. A set of pipes are inserted through the holes in the upper plate and the corresponding holes in the lower plate, and are sealingly brazed to both plates. Cooling channels may be provided in the lower plate.