JPS6453463A - Semiconductor nonvolatile storage element - Google Patents

Abstract

PURPOSE:To obtain a storage element sufficient in a write-in data property without increasing a cell area by a method wherein a trench provided to a substrate is utilized not only as an element isolation region but also as a region which increases capacitance between a control gate and a floating gate. CONSTITUTION:An insulating film 120, which is thicker than a gate insulating film 108, is formed on a wall face 118 of a trench 116 provided to a substrate 100 as a field oxide film, connecting with the gate insulating film 108. And, a floating gate electrode 110, an inter-electrode insulating film 112, and a control gate 114 are formed on the insulating film 120 of the sidewall of the trench 116, being extended from their own part on a channel region 106. In such an EPROM cell structure, a channel current flows through the substrate 100 under the gate oxide film 108. Channel hot electrons generated during the write-in of data are injected into the floating gate 110 passing through the gate oxide film 108.