Based on appropriate down scaling of devices and reasonable extrapolation of present technological possibilities, circuit performance of several LSI technologies has been calculated. From a set of impurity distributions, oxide thickness, etc., process parameters have been derived, which have been converted into transistor-model parameters for use in a circuit simulation program. Although for every technology a substantial improvement in performance is predicted, MOS appears to benefit most from scaling down. The speed of ED-MOS eventually rivals that of ECL and the speed-power product that of I2L. Below 1 µm gate width a delay time of 100 ps and a speed-power product of 20 f J are possible. I2L is by far the slowest technology, but it has the best packing density. Current densities in MOS approach that of ECL. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.