In this paper, various process conditions of tunnel oxides are applied in SONOS flash memory to investigate then effects on charge transport during the program/erase operations We focus the key point of analysis oil Fermi-level (E(t)) variation at the interface Of Silicon Substrate and tunnel oxide The Si-O chemical bonding information which describes the interface oxidation states at the Si/SiO(2) is obtained by the core-level X-ray photoelectron spectroscopy (XPS) Moreover. relative Er position is determined by measuring the Si 2p energy shift from XPS spectrums Experimental results from memory characteristic measurement show that MTO tunnel oxide structure exhibits faster erase speed, and larger memory window during PIE cycle compared to FTO and RTO tunnel oxide structures. Finally, we examine long-term charge retention characteristic and find that the memory windows of all the capacitors remain wider than 2 V after 10(5) s (C) 2009 Elsevier B V All rights reserved