 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).By 1974, charge trap technology was used as a storage mechanism in electrically erasable programmable read-only memory (EEPROM), and was an alternative to the standard floating-gate MOSFET technology.In 1977, P.C.Y.