Atomic force microscopy (AFM) has been used to fabricate and electrically characterize SiO2 films as gate dielectrics of metal-oxide-semiconductor (MOS) electronic devices. The electrical properties of the AFM grown oxide (3 nm thick) have been determined at a nanometric scale and compared to those of thermal gate oxides (GOXs). The results show a similar electrical behaviour of both kinds of oxide. Furthermore, the broken down GOX locations (breakdown spots) induced in microelectronic-sized devices have been located and electrically characterized with AFM. The results indicate that AFM is a suitable tool for the fabrication and reliability analysis of present and future Si/SiO2 based MOS nanoelectronic devices.