Treatment using water dissolved highly ozone (ozonated-water) was investigated to eliminate organic contaminations from the surface of silicon wafer. In order to enhance a concentration of ozone in ozonated-water, impurity soluble in ultra pure water, especially CO2, was found to be significant. It is presumed that such impurity plays the role of inhibitor to suppress decomposition of O-3. The ozonated-water dissolved ozone of 100 mg/l and above showed excellent properties to eliminate resist as typical model of organic contaminants. It was found that the elimination rate of resist depends not on coexistence of H2O2 but on temperature of ozonated-water. (C) 2007 Elsevier Ltd. All rights reserved.