Most conventional chemical vapor deposition (CVD) systems do not have the spatial actuation and sensing capabilities necessary to control deposition uniformity, or to intentionally induce nonuniform deposition patterns for single-wafer combinatorial CVD experiments. In an effort to address these limitations, a novel CVD reactor system has been developed that can explicitly control the spatial profile of gas-phase chemical composition across the water surface. This paper discusses the simulation-based design of a prototype reactor system and the results of preliminary experiments performed to evaluate the performance of the prototype in depositing tungsten films. Initial experimental results demonstrate that it is possible to produce spatially patterned wafers using a CVD process by controlling gas-phase reactant composition, opening the door to a new class of flexible and highly controllable CVD reactor designs. (C) 2005 American Institute of Chemical Engineers.