Generation of electrolytic ionized water (EIW) from chemical mechanical polishing (CMP) wastewater using a simultaneous crossflow electrofiltration/electrodialysis process was studied in this work. In the semiconductor industry, presently, CMP has become the key technique to provide global planarization on interlevel dielectrics and metal layers of wafers. In general, post-CMP cleaning requires a huge volume of ultrapure water (UPW) to remove foreign materials from the wafer surfaces. An almost the same amount of CMP wastewater thus would be generated. Therefore, treatment and reclamation of CMP wastewater is significant and important. In this study, a multi-membrane set has been incorporated into a crossflow electrofiltration/electrodialysis treatment module for treating a mixed CMP wastewater and simultaneously generating two streams of electrolytic ionized water, which has several extraordinary characteristics. Experiments were carried out based on the 2(4-1) fractional factorial design using four experimental factors to investigate their effects on the permeate qualities. After treatment, each stream of permeate has a turbidity of below 1 NTU, total organic carbon of below 3 mg/l, and total dissolved solids of below 50 mg/l. Besides, permeate has a much smaller size of water molecule cluster than that of tap water according to the O-17 NMR (nuclear magnetic resonance) relaxation measurements. Thus, EIW obtained in this study is suitable for high-level recycling. (C) 2004 Elsevier B.V. All rights reserved.