A Monte Carlo simulator was developed to simulate the profile evolution during the Cl etching of patterned polysilicon in high density plasma etchers. The simulator used Monte Carlo techniques to compute the transport and surface kinetics combined with a cellular representation of the feature. The Monte Carlo algorithm permitted the incorporation of all the dominant physical and chemical mechanisms of the etching process such as angle-dependent ion-enhanced etching, physical sputtering, ion scattering, surface recombination, plasma deposition, sidewall passivation, and line-of-sight redeposition without encountering numerical difficulties. The technique allows for the modification of surface kinetics rates based on the surface composition. Simultaneous composition-dependent etching and deposition could be handled easily. A modification of the cellular representation of the feature (similar to a string-and-node algorithm) was developed to determine neutral species interactions with the surface enabling accurate Simulation of deposition processes. A surface normal calculation algorithm involving least-squares fitting of the surface was developed to handle specular ion scattering. A generalizable structure allowing the incorporation of all chemical and physical processes was developed to handle the compositional, energy, and angular dependent surface processes. Test cases were run to quantify the accuracy of the combined Monte Carlo and cellular algorithms.