SONOS

SONOS, short for "silicon–oxide–nitride–oxide–silicon", more precisely, "polycrystalline silicon"—"silicon dioxide"—"silicon nitride"—"silicon dioxide"—"silicon",^: 121 is a cross sectional structure of MOSFET (metal–oxide–semiconductor field-effect transistor), realized by P.C.Y. Chen of Fairchild Camera and Instrument in 1977. This structure is often used for non-volatile memories, such as EEPROM and flash memories. It is sometimes used for TFT LCD displays. It is one of CTF (charge trap flash) variants. It is distinguished from traditional non-volatile memory structures by the use of silicon nitride (Si₃N₄ or Si₉N₁₀) instead of "polysilicon-based FG (floating-gate)" for the charge storage material.^{: Fig. 1} A further variant is "SHINOS" ("silicon"—"hi-k"—"nitride"—"oxide"—"silicon"), which is substituted top oxide layer with high-κ material. Another advanced variant is "MONOS" ("metal–oxide–nitride–oxide–silicon").^{: 137 : 66} Companies offering SONOS-based products include Cypress Semiconductor, Macronix, Toshiba, United Microelectronics Corporation and Floadia.