The silicon dioxide (SiO2) film was fabricated from layer-by-layer depositing amorphous silicon (a-Si) film combined with step-by-step plasma oxidation in the plasma-enhanced chemical vapor deposition (PECVD) system. The capacitance-voltage(C-V) and conductance-voltage(G-V) characteristics show that the fixed charge and interface state densities of the SiO2 film are 9×1011 cm-2 and 2×1011 cm-2·eV-1, respectively. Furthermore, the breakdown field strength is as high as 4.6 MV/cm, which is comparable to that formed by hot oxidation. The prepared SiO2 is employed as control oxide in nc-Si based double-barrier floating gate memory structure and is found to be an effective way to prevent the charge exchange between the gate electrode and nc-Si, which also lead to an enhancement in the retention time. The improved performance of the memory is discussed and is ascribe to the moderate-thickness of SiO2 as well as its excellent electrical properties.