Using Si samples with 400-nm-wide alternately high and low doped p-type layers on p-type substrate, we investigate the dependence of the scanning capacitance microscope (SCM) signal amplitude as a function of oxide thickness and dopant concentration. The oxide layers were created by a standard industrial high temperature oxidation process. Together with the implementation of the newly developed conductive diamond tips, good and quantitatively reproducible contrast for differently doped domains is obtained on all samples. A comparison with conventional metal-oxide-semiconductor theory shows good correlation for the decrease of the capacitance signal with increasing insulator thickness and increasing dopant concentration. Furthermore, geometry effects, such as the influence of the domain width on the SCM signal, are discussed.