An investigation of the effect of thermal annealing and anodization parameters, such as the electrolyte pH and current density, on capacitance-voltage and interface state density distribution characteristics has been made. Al(anodic oxide) SiO2/p-Si MOS structures were prepared: in 0.1 M K2SO4 electrolyte with a pH of 7 (the 0.1 M KOH solution was buffered with H2SO4) at current densities of 3, 5, and 7 mA/cm(2) and with four different pH; values of the electrolyte at 3 mA/cm(2). It is found that thermal annealing a relatively low temperature can be used to improve the anodic MOS characteristics. Moreover, of the pH and current density it followed that the pH has a dominant role in the interface electrical properties. The lowest interface state densities at the maximum and the midgap positions are 7.1 x 10(11) and 2.7 x 10(10) eV(-1) cm(-2) for a sample made with pH = 7, J = 3 mA/cm(2). The characteristics of this sample seem satisfactory for device applications of anodized p-Si.