We have used a scanning tunneling microscope to locally modify thin oxide films on silicon. Current‐voltage (I‐V) measurements were performed on these samples and compared with those on ‘‘as‐polished’’ (mechanically and chemically polished by the manufacturer). We found that theI‐Vmeasurements on samples with thin oxide films were nearly symmetric, characteristic of metal‐oxide‐semiconductor structures dominated by interface states. In contrast, we observed band‐bending on the ‘‘as‐polished’’ samples. The thin oxide film directly under the tip was modified by application of a voltage pulse. This change was reflected in theI‐Vmeasurements.