Charge traps and interface traps in ONO (Oxide-Nitride-Oxide) structures fabricated on Si (001) substrates have been investigated. Nitride-related traps are observed to be located in the range of 2.44-2.48 eV above the valence band maximum of the nitride layer. It is demonstrated that the capacitance transient spectroscopy method could be a tool to evaluate properties of the tunneling oxide and the nitride effect on interface states. (c) 2008 Elsevier B.V. All rights reserved.