disclosed is a process of treating semiconductor substrates , including the production of pure water , a method of producing the pure water for semiconductor fabrication , and a water - producing apparatus . ammonia is catalytically oxidized in a catalytic conversion reactor to form pure water . the water is then supplied to a semiconductor fabrication process . the water - producing apparatus comprises a housing surrounding a catalytic material for adsorbing ammonia , an ammonia and oxidant source , each in communication with the housing , and an outlet for reaction products . the outlet is connected to a semiconductor processing apparatus . according to preferred embodiments of the invention , the apparatus can be a catalytic tube reactor , a fixed bed reactor or a fluidized bed reactor . this process and apparatus allows the quantity of unreacted excess oxidant to be limited , preventing undesired oxidation of low oxidation resistant metal gate electrodes during semiconductor fabrication processes , such as during wet oxidation processes like source / drain reoxidation . at the same time , the use of ammonia reactants lessens the risk of dangerous explosions and excessive boron diffusion while fabricating surface p - channel semiconductor devices .