The charge trapping behavior of SiON thin films using various processing methods are studied. The transient analysis method [Lue HT, Shih YH, Hsieh KY, Liu R, Lu CY. A transient analysis method to characterize the trap vertical location in nitride-trapping devices. IEEE Electron Dev Lett 2004;25:816-8] reveals that SiON has a higher capture efficiency than SiN so that gate injected electrons are mostly stopped at the interface between top oxide and trapping layer, independent of whether the SiON is formed by thermal oxidation of SiN or direct LPCVD deposition. On the other hand, the excess Si piling-up behavior is observed during oxidation process over SiN, and it shows correlation with the native negative charge. Therefore, the effect of excess Si piling-up and SiON trapping layer are discriminated for the first time. (c) 2006 Elsevier Ltd. All rights reserved.