The presence of an interface can impose distinct local conditions that can have an important influence on the outcome of a chemical reaction at a nanoscale level. Loosely, two broad types of phenomena can be identified. In one, the interface can serve as an impermeable structure that imposes concentration gradients on materials in contact with it, leading to measurably different chemistry than would occur in its absence. In the other, the interface can serve as a means of accelerating transport, building in significant blur to the contacted regions. Semiconductor fabrication processes are influenced by one or both, directly controlling how well methods developed for the microscale can be adapted to the nanoscale. Examples drawn from etching, deposition, photolithography and nanoimprint lithography will be discussed, illustrating some general principles that may potentially be used to advantage in materials nanoprocess design.