A process and a configuration for producing ultra-pure water for a semiconductor manufacturing plant containing a plurality of manufacturing units. In a first purification step, untreated water undergoes preliminary purification in amounts required for the plant. In a plurality of final purification units, which are each assigned to at least one manufacturing unit, ultra-pure water of a stipulated quality is obtained from a treated water in a second purification step as a function of the process parameters of the associated manufacturing unit.