We applied thermally stimulated exoelectron emission (TSEE) and thermally stimulated luminescence (TSL) methods for trap spectroscopy studies of ultrathin amorphous Si3N4 films used in ONO (oxide/nitride/oxide) structure-based microFlash memory devices. The temperature spectra of TSEE of the films demonstrate two groups of TSEE peaks: three low temperature peaks (T-1 = 383 K, T-2 = 393 K, T-3 = 413 K) and a high temperature maximum at T-4 = 813 K. The developed Auger model of TSEE allowed calculating trap energy spectrum responsible for the TSEE peaks generation. TSEE results are shown to be consistent with trap energy activation Phi estimates obtained from microFLASH(R) two bit per cell memory transistor measurements where electrons stored at deep traps are responsible for high temperature TSEE peak with Phi(4) = 1.73 eV. We believe that deep traps in silicon nitride are hydrogen containing centers. TSEE studies of the high temperature decay process of these traps explain excellent retention properties of microFlash memory devices. (C) 2003 Elsevier Ltd. All rights reserved.