Abstract: Reactor-scale computer simulations of inductively and capacitively coupled plasmas are developed in FEMLAB and Matlab to describe processing plasmas. The expectation is that the new models will be more easily maintained and transferred than existing 'home-built' codes. The dissertation presents results describing inductively and capacitively coupled plasmas as well as investigating fluid flow and chemistry. A model is used to investigate the effect of a simulated high-density plasma on the neutral pressure profile for various flow rates and configurations. Neutral gas flow in non-equilibrium, high-density plasmas can be significantly complicated by gas heating and molecular dissociation. The results show that the neutral pressure and therefore neutral density profiles are dictated by the fluid dynamics of the system interacting with the plasma. For a fixed flow rate of gas through a tube, plasma heating and dissociation can greatly increase the pressure drop through the plasma region. We show that this pressure drop is due primarily to the effects of increased mass-average gas velocity that result from a decrease in mass density. Similar calculations for gas flowing into a large chamber demonstrate that for conditions of general interest in plasma processing, the gas pressure in the chamber is usually near-constant, except near the in-flow and out-flow regions of the chamber. With near supersonic gas velocity in the in-flow tube, the effects of flow on gas temperature and composition near the in-flow tube can be significant. Furthermore, a local rise in pressure and a significant alteration of the gas flow pattern within the chamber is observed. In addition, a simulation is presented investigating the lifecycle of fluorocarbons in an argon dominated inductively coupled discharge. In plasma modeling, physical data such as gas phase reactions and collision cross sections are often unknown or uncertain at best. The simulation was used to validate available gas-phase chemistry models for c-C₄F ₈ by direct comparison with experiments performed by Cheng-Che Hsu in an argon-rich plasma in a diagnostic ICP chamber. Furthermore, these experiments suggest that a significant portion of the inlet fluorocarbon gas may deposit on the chamber walls. Thus, this work also explores the effect of including surface reactions, both neutral and ionic, under the conditions of interest. The results demonstrate that a dramatic change in neutral and ionic composition is obtained when surface reactions are included. (Abstract shortened by UMI.)