This article will review the achievements, on-going development activities and needs in "equipment support technology," i.e., the critical or key components which surround the process chamber and without which an effective process cannot be reliably and repeatably executed. The challenges of the SIA (Semiconductor Industry Association) Roadmap have been the focus for the dramatic developments in many areas, such as the following : delivery of process material vapors into the reactor, control of the exhaust effluent from the reactor, on-process pressure measurement and control sensors and actuators, implementation of a well supported digital sensor bus introduced on 300 mm tool sets, tool and process diagnostics through residual gas analysis, and the incorporation of fault detection schemes and the eventual implementation of model based process control techniques. With the escalating cost of wafers-in-process, and the desire to increase overall equipment effectiveness and reduce cost-of-ownership, it becomes increasingly important to separate, control, diagnose and predict the behavior of critical process variables in real time. In-situ measurement, control, and metrology result in dramatically improved meantime between failures, shorter meantime to repair, and a significantly reduced cost per measurement function.