The optical charge pumping (CP) technique is proposed as a simple and fast method for extracting the energy distribution of interface trap, Dit, of silicon-oxide-nitride-oxide-silicon (SONOS) flash memories. It is based on the optical response of a subthreshold slope of a SONOS memory cell transistor and is more effectively applicable to nano-scale emerging devices than the conventional CP technique, because no electrical pulse is required during extraction and because the current is measured not from the substrate, but from the drain contact. This means that a large gate current can be easily corrected by monitoring both the gate current and the drain current, no parasitic effect is caused by excluding the pulse measurement setup, and the extraction of Dit in devices on silicon-on-insulator substrates is possible. The results applied to SONOS memories show that the generation rate of interface traps with program/erase cycles is higher in the NAND flash scheme rather than in the NOR flash scheme.