The local oxide defects observed in thin silicon dioxide films onp‐type Si were studied with the electron beam induced current/tunneling current microscopy technique. Excluding pinholes, all the local defects observed are local oxide/substrate defects, i.e., local oxide defects propagated from defects in the Si substrate into the SiO2. It was observed that local oxide/substrate defects can be further differentiated into two different types by studying the transition from the true oxide electron beam induced current contrast to the tunneling current microscopy contrast. ©1995 American Institute of Physics.