Non-Arrhenius behavior has been reported in a various temperature range for the retention time of CT Flash memories. In order to understand the physical origin of the multiple activation energy due to the non-Arrhenius behavior, we conduct a simulation study using a 3D self-consistent numerical simulator developed in-house. As a result, it is found that both vertical and lateral charge transport in the conduction band of nitride layer are responsible for the non-Arrhenius retention characteristic. Also, the tunneling current through the bottom oxide and a lifetime criteria are turned out to be the key parameters which determine the multiple activation energy. (C) 2015 Elsevier Ltd. All rights reserved.