In this study, experiments were performed to investigate phosphorus deactivation in polysilicon and a deactivation model was proposed to improve the simulation of nanometer memory devices. Decay of carrier concentration was observed during low-temperature annealing in polysilicon films formed by different methods. However, the decay rate decreased with time and the carrier concentration almost saturated after long-term annealing. The grain size of polysilicon did not significantly affect the decay of carrier concentration. A clustering model was proposed to simulate the deactivation. The model assumes that the cluster formation rate dominates the dependence of the deactivation process on temperature. Direct reactions between neighboring phosphorus atoms was suggested to explain the rapid deactivation with a high initial activation level. The impact of deactivation on the electrostatics of memory devices was demonstrated by simulation using the proposed clustering model. (C) 2012 Elsevier Ltd. All rights reserved.