Trench isolation method

Abstract

A method of forming trench isolated integrated circuitry on a substrate provides a substrate having a first insulating material within and projecting from an isolation trench and a second insulating material laterally proximate the first insulating material. The second insulating material is etched substantially selective relative to the first insulating material to expose substrate beneath the second insulating material. After the etching, a gate dielectric layer is formed over the exposed substrate. A transistor gate is formed over the gate dielectric layer. In but one other implementation, an oxide layer is thermally grown over a semiconductive substrate. An isolation trench is formed through the thermal oxide layer and the semiconductive substrate. Oxide is deposited within the trenches and formed to project outwardly relative to the thermal oxide. The thermally grown oxide is etched substantially selective relative to the deposited oxide to outwardly expose the semiconductive substrate and provide deposited oxide within the isolation trench which projects outwardly of the substrate. The semiconductive substrate and projecting deposited oxide have an interface therebetween which is substantially void of any recess of the deposited oxide below the semiconductive substrate. After the etching, gate oxide is grown over the substrate and the interface. A transistor gate is formed over the gate oxide over the semiconductive substrate.