Chemical mechanical polishing (CMP) is the most effective technology for global planarization in submicrometer device fabrication. Therefore, much research has been conducted to understand the basic mechanisms of the CMP process. In this study, a model that considers the microcontact mechanism and the grain flow is proposed. The down force acting on the wafer is supported by both the slurry pressure in the noncontact area and the surface asperity contact force in the contact area. The operation parameter effects on the force distribution, separation distance, and real contact area were investigated. The results show that larger down force and lower relative speed between the wafer and the polishing pad lead to increased contact ratio between the polishing interfaces. Larger slurry particle size can decrease the contact ratio. (C) 2003 The Electrochemical Society.