Magnetic-core memory was developed from the research of Frederick W. Viehe in 1947 and An Wang at Harvard University in 1949. With the advent of the MOS transistor, MOS semiconductor memory was developed by John Schmidt at Fairchild Semiconductor in 1964. In 1967, Dawon Kahng and Simon Sze at Bell Labs described in 1967 how the floating gate of an MOS semiconductor device could be used for the cell of a reprogrammable ROM. Following the invention of flash memory by Fujio Masuoka at Toshiba in 1980, Toshiba commercialized NAND flash memory in 1987.