the converse problem however, where electrons become strongly trapped in the ONO layer and cannot be removed again. Over long usage this can eventually lead to enough trapped electrons to permanently set the cell to the "0" state, similar to the problems in flash. However, in SONOS this requires on the order of a 100 thousands write/erase cycles, 10 to 100 times worse compared with legacy FG memory cell. History Background The original MOSFET (metal–oxide–semiconductor field-effect transistor, or MOS transistor) was invented by Egyptian engineer Mohamed M. Atalla and Korean engineer Dawon Kahng at Bell Labs in 1959, and demonstrated in 1960. Kahng went on to invent the floating-gate MOSFET with Simon Min Sze at Bell Labs, and they proposed its use as a floating-gate (FG) memory cell, in 1967. This was the first form of non-volatile memory based on the injection and storage of charges in a floating-gate MOSFET, which later became the basis for EPROM (erasable PROM), EEPROM (electrically erasable PROM) and flash memory technologies. Charge trapping at the time was an issue in MNOS transistors, but John Szedon and Ting L. Chu revealed in June 1967 that this difficulty could be harnessed to produce a nonvolatile memory cell. Subsequently, in late 1967, a Sperry research team led by H.A. Richard Wegener invented the metal–nitride–oxide–semiconductor transistor (MNOS transistor), a type of MOSFET in which the oxide layer is replaced by a double layer of nitride and oxide. Nitride was used as a trapping layer instead of a floating gate, but its use was limited as it was considered inferior to a floating gate. Charge trap (CT) memory was introduced with MNOS devices in the late 1960s. It had a device structure and operating principles similar to floating-gate (FG) memory, but the main difference is that the charges are stored in a conducting material (typically a doped polysilicon layer) in FG memory, whereas CT memory stored charges in localized traps within a dielectric layer (typically made of silicon nitride). Development SONOS was first conceptualized in the 1960s. MONOS is realized in 1968 by Westinghouse Electric Corporation. In the early 1970s initial commercial devices were realized using PMOS transistors and a metal-nitride-oxide (MNOS) stack with a 45 nm nitride storage layer. These devices required up to 30V to operate. In 1977, P.C.Y. Chen of Fairchild Camera and Instrument introduced a SONOS cross sectional structured MOSFET with tunnel silicon dioxide of