Self aligned method for differential oxidation rate at shallow trench isolation edge

摘要

A semiconductor process in which at least one isolation structure is formed in a semiconductor substrate is provided. An oxygen bearing species is introduced into portions of the semiconductor substrate proximal to the isolation structure, preferably through the use of an ion implantation into a tilted or inclined substrate. A gate dielectric layer is then formed on an upper surface of the semiconductor substrate. The presence of the oxygen bearing species in the proximal portions of the semiconductor substrate increases the oxidation rate of the proximal portions relative to the oxidation rate of portions of the substrate that are distal to the isolation structures. In this manner, a first thickness of the gate dielectric over the proximal portions of the semiconductor substrate is greater than a second thickness of the gate oxide layer over remaining portions of the semiconductor substrate. The increased oxide thickness adjacent to the discontinuities of the isolation trench reduces the electric field across the oxide.