The article presents the results of STM investigations of the Si-SiO2 and Si-SiO2-polymer systems in air. Depending on the scanning parameters, such as the collage applied and tunneling current, a modification of the Si-SiO2 surface was observed during these experiments. The possibility of the reversible modification was demonstrated. A thin polymer film was used to exclude the adsorption-desorption anti electrochemical processes on the Si surface. The modification of the Si-SiO2-polymer surface was observed at the scanning parameters similar to those for the modification of the Si-SiO2 system. The electronic mechanism of the surface modification based on the tunneling of a charge through the oxide layer and its influence on the STM tunneling current is discussed.