This publication investigates the program simulation of charge trapping memory devices in detail. Three different aspects of the simulation are highlighted which have a major impact on the program characteristics in trap based memories. The analysis is done by a comparison between measurement and simulation. It is shown that the trap capture cross section, the bottom oxide to storage nitride energy band offset and the tunneling injection point, under modified Fowler-Nordheim tunneling conditions, are of major importance for highly accurate simulations. The results provide deeper insight into the mechanisms dominating the program behavior in charge trapping memory devices.