Automated and thorough characterization of MOS transistors has been made possible by using a minicomputer-based instrumentation system. A low-current circuit capable of forcing current levels down to the range of 10 pA has been designed on the personality board, allowing fast measurements of subthreshold characteristics. A comprehensive test program has been developed to extract device parameters, such as threshold voltage, subthreshold slope, intrinsic mobility, mobility degradation, effective-channel doping, body effect, ΔL, ΔW, series resistance, and carrier-saturation velocity. Data management software also provides detailed statistical analysis. The technique is found to be a powerful and essential tool for VLSI process development.