Method for erasing data in a semiconductor memory device

Abstract

The invention concerns a method for electrically erasing data stored in a FAMOS-type EPROM. That is, in an Electrically Programmable Read Only Memory of the Metal Oxide Semiconductor type in which a Floating gate is employed as a memory element and in which data-writing is effected by charge injection from a channel Avalanche current, the invention concerns a method for effectively removing such channel-injected charge from a subject written floating gate. The method specifically entails the injection into the written gate of neutralizational opposing-polarity hot carriers from a generated reverse avalanche current between th MOS drain and substrate. The drain avalanche, however, is limited to 'non-breakdown' levels by a technique which, in addition to appropriate drain biasing, includes suitable source and control-gate biasing so as to essentially prevent the flow of channel current during erasure. The method is applicable to either n-channel or p-channel devices and does not require the use of a separate select transistor.