Factors affecting the slope of the reactive ion etched molybdenum line have been studied with a simulation method and with experiments. Plasma chemistry and process parameters of the CF4/O2 mixture for the molybdenum etch have been examined. The theoretical calculation matches experimental results. Surface topography and composition of the etched molybdenum have been analyzed. A highly sloped molybdenum profile can be obtained by using the RIE method with a large process window. © 1990, The Electrochemical Society, Inc. All rights reserved.