The SiO2/nanocrystalline silicon (nc-Si)/SiO2 double-barrier structure on p-type (1 0 0) silicon substrate was fabricated in situ by plasma oxidation and layer-by-layer deposition at low temperature (250 ℃) in a plasma enhanced chemical vapor deposition reactor. Frequency-dependent capacitance-voltage measurements were performed to study the electrical properties and the results can be explained by schematic band diagrams and equivalent circuits. Single electron charging effect (corresponding to the two capacitance peaks) in large ensemble of nc-Si dots (~10(9)) was observed at room temperature, which demonstrates that the Coulomb blockade energy in nc-Si dots is larger than room thermal energy kBT and the nc-Si size fluctuation effects on the quantum confinement of this SiO2/nc-Si/SiO2 structure.