Very thin SiO2 films (3-6 nm) have been characterized with a conductive atomic force microscope (C-AFM). The set-up allows the electrical characterization of 30-50 nm2 areas, which are of the order of single breakdown spots. Voltage ramps have been repeatedly applied to induce the degradation. On these spots, the phenomenology observed is quite similar to that during conventional electrical tests. In particular, on-off fluctuations before and after breakdown are reported on single breakdown spots. The results confirm the C-AFM as a suitable tool for the analysis of the gate oxide electrical properties and degradation dynamics at a nanometer scale. © 2001 Elsevier Science Ltd. All rights reserved.