Contact pressure and flow features of chemical mechanical polishing/planarization (CMP) process were analyzed,taking advantage of the one-dimensional contact model of two layers and considering slurry flows. In this model,deformations of the bulk pad substrate and the asperities were considered. The deformations of the bulk pad sub- strate and the asperity layer,as well as the contact pressure and fluid pressure,were revealed with nu- merical methods. Numerical simulation results show a counterintuitive phenomenon: a diverging clear- ance is formed in the leading region of the wafer and thereby it gives rise to a suction pressure (subambi- ent pressure). A high stress concentration is pre- sented at the wafer edge and thereby over polishing can be introduced. The research provides some theoretical explanations for these two fundamental features of usual CMP processes. Contact pressure and flow features of chemical mechanical polishing / planarization (CMP) process were analyzed, taking advantage of the one-dimensional contact model of two layers and considering slurry flows. In this model, deformations of the bulk pad substrate and the aspersities were considered . The deformations of the bulk pad sub- strate and the asperity layer, as well as the contact pressure and fluid pressure, were revealed with nu-merical methods. Numerical simulation results show a counterintuitive phenomenon: a diverging clear- ance is formed in the leading region of the wafer and therefore it gives rise to a suction pressure (subambi ent pressure). A high stress concentration is pre- sented at the wafer edge and therefore over polishing can be introduced. The research provides some theoretical explanations for these two fundamental features of usual CMP processes.