Electronic properties and morphology of the multiple Si-SiO2 quantum wells (MQWs), deposited on top of vicinal Si(001) substrate are studied by DC-electric field induced second harmonic generation (SHG). Non-linear contribution is associated with offset structure of the silicon layers of MQWs. Regular oscillations of the SHG intensity in the DC-electric field domain are observed. This oscillatoric SHG dependence stems from the non-monotonic dependence of the DC-electric held on the external bias voltage applied to the multilayer structure. The mechanism behind this phenomenon is essentially related to quantum confinement effects in 2D silicon layers.