A simple analytical expression is derived for charge retention in MNOS memory devices assuming that retention loss is limited by Frenkel‐Poole release from monoenergetic traps. This model shows that charge retention becomes eventually independent of the initial charge distribution. Experimental data obtained at elevated temperatures confirm this model and provide a trap depth of 1.5 eV, Frenkel‐Poole coefficient of about 6×10−4cm1/2 V−1/2 eV, and effective escape attempt rate factor of 1.2×108sec−1.