Capacitance-voltage was investigated for amorphous silicon quantum dots (a-Si QDs) embedded in a silicon nitride as a function of dot size and nitride thickness. a-Sci QDs were grown by plasma enhanced chemical vapor deposition. The electron charging was decreased as the dot size was decreased. These results showed that the conduction band shift is larger than the valence band shift as the dot size decreased and, as a result, electrons are easily discharged in a-Si QDs due to the lower barrier height. For high dot-density-sample, the capacitance-voltage curves were also shifted toward the negative voltage direction when a higher forward bias was applied at forward condition due to the transfer of electrons trapped in the a-Sci QDs from the a-Sci QDs near Si substrate to those near the top metal.