Electrically erasable read only memory

Abstract

An electrically erasable floating gate storage cell (EPROM) is disclosed which comprises a body of single crystal silicon semiconductor material having a substrate of one conductivity type, a source region and a drain region each of a second conductivity type, a channel region of the first conductivity type connecting the source region and drain region, a polycrystalline silicon layer conductively connected to either the source region or the drain region, a conductive insulated floating gate which partially overlies and is separated from the polycrystalline silicon layer by a layer of silicon dioxide and a control gate which overlies and is separated from the floating gate by a layer of silicon dioxide. Fowler-Nordheim tunneling current occurs between the polycrystalline layer and the floating gate during programming and erasing of the EPROM. The floating gate influences the conductivity of the channel region in accordance with the charge stored thereon during programming. The control gate is oriented over the entire channel region to control the conductivity of the channel region in accordance with voltages applied thereto during operation of the EPROM.