Vmos floating gate memory with breakdown voltage lowering region

Abstract

A semiconductor electrically programmable read only memory device (EPROM) utilizes an array of memory cells each in the form of a single V-type MOSFET which achieves the normal AND function (Data-Word Address) using a capacitance coupled version of threshold logic. Each MOSFET is formed by a V-shaped recess at the intersection of each bit line and word line that extends across the diffused bit line, (which serves as the transistor drain) and into the substrate (which serves as the source and ground plane of the device). A similarly V-shaped floating gate is isolated below and above the crossing bit and word lines by thin oxide layers. A ring of P-type conductive material around the upper end of each V-shaped recess and adjacent its surrounding N-type drain region serves to lower the required programming voltage without increasing the device threshold voltage.