The current trend in the semiconductor industries is to move the reliability tests usually performed at he end of the process flow, towards in the in line monitors. This need opens a new strategic direction for the scanning probe microscopy, permitting to avoid dedicated sample preparation. Among the examples of SPM-scanning tunneling microscope, near-field scanning optical microscope, atomic force microscope, scanning thermal microscope and scanning capacitance microscope - some of them are still under investigation. In this paper a new scanning capacitance microscope able to perform quantitative local in-situ monitor of the silicon oxide properties is being established. The test samples used in this work, were p- doped silicon wafers with a 10 nm oxide layer thermally grown. The tip of the microscope, brought into contact with the sample surface, is biased with a voltage stairs, so local frequency-voltage (F-V) measurements can be performed. Another configuration of the equipment, which allows to measure the flat band voltage of the MOS capacitor as the peak of the derivative F-V curves, is also presented. The measurements methods described above have been compared with standard C-V measurements showing an alternative way to investigate on the presence of defects inside SiO2 without requiring any sample preparation.