The use of scanning kelvin probe microscopy (SKPM) for analyzing two-dimensional dopant profiles on production-level silicon CMOS devices is described, with images of topography and dopant profiles presented. Both plan-view and crosssectional analyses are performed to measure CMOS device effective channel length (Leff), source-drain and well-junction depths. SKPM data not only tracked variations in Leff but uncovered anomalies in dopant that were responsible for device failure. For example, a nonfunctional ring-oscillator in a 0.25μm technology was debugged with SKPM. Details of sample preparation and the fabrication of durable, highly conductive (silicided) silicon kelvin probe tips which are key to acquiring reproducible, consistent data is also given.