Doubly stacked layers of amorphous silicon (a-Si) between amorphous silicon nitride (a-SiNx) layers have been fabricated by plasma enhanced chemical vapor deposition (PECVD)technique. Si nanocrystal (nc-Si) layers were formed by thermal crystallization of a-Si layers after a furnace annealing at 1100℃ for 30 min in N2 ambient. The phenomena of charge trapping and storage in nc-Si layers were observed in both capacitance-voltage (C-V) and current-voltage (I-V) measurements at room temperature. The structure has revealed a double-level charging process. Two stages of charge storage were evident in the series of C-V curves. The phenomena and mechanism of charge storage were discussed in detail.