The interfacial layer theory considering the surface fixed charge and the voltage drop across the interfacial layer is developed for the Schottky barrier diodes fabricated on then‐type semiconductor substrate. It is shown that the positive surface fixed charge will reduce the barrier height and then increases the reverse current; the voltage drop across the interfacial layer will increase the ideality factor of the forward biasedI‐Vcharacteristic and the voltage dependence of the reverse‐biasedI‐Vcharacteristic, aside from the effects of the image force lowering; the fluctuations of the experimental data deduced from the fabricated Schottky barrier diodes with different fabricating conditions are mainly due to the variations of the interfacial‐layer properties such as the interfacial‐layer thickness, the interface states, the surface fixed charges.