- The effect of double programming (DP) on the retention of two-bit SONOS memory devices is studied. After the first programming and bake, the memory cell is programmed again to the Vtbefore bake. Computer simulations of DP operations show that the electrons trapped outside the injection region (IR) create an electric field that prevents lateral spreading of injected electrons. Improved high temperature retention after the second programming and bake is observed: the Vtshift after the second programming is half of what it is after the first programming. Simulation results are in agreement with experimental data.