The invention relates to a method and system for cleaning semiconductor elements accommodated in a tank which uses ozonized, deionized (DI) ultrapure water. According to the invention, ozone is generated in an ozone generator (3) according to the principal of silent electric discharge while admitting highly pure oxygen. Said ozone is fed to a contactor (7) through which DI water flows. The ozone is then dissolved in the DI water. While optionally admitting additional chemicals, the ozonized DI water is conducted through the tank (12) holding the semiconductor elements in order to clean the same, and the used DI water is carried away (15). In order to stabilize the ozone concentration, CO.sub.2 is added to the ozone/oxygen mixture generated by the ozone generator (7).