We examine the electrical properties of metal/oxide/nitride/oxide/silicon (MONOS) capacitors with two different blocking oxides, SiO(2) and Al(2)O(3), under the influence of the same electric field. The thickness of the Al(2)O(3) layer is set to 150 angstrom, which is electrically equivalent to a thickness of the SiO(2) layer of 65 angstrom, in the MONOS structure for this purpose. The capacitor with the Al(2)O(3) blocking layer shows a larger capacitance-voltage memory window of 8.6 V, lower program voltage of 7 V, faster program/erase speeds of 10 ms/1 mu s, lower leakage current of 100 pA and longer data retention than the one with the SiO(2) blocking layer does. These improvements are attributed to the suppression of the carrier transport to the gate electrode afforded by the use of an Al(2)O(3) blocking layer physically thicker than the SiO(2) one, as well as the effective charge-trapping by Al(2)O(3) at the deep energy levels in the nitride layer. (C) 2009 Elsevier B.V. All rights reserved.