Lateral diffusion field effect transistor with asymmetric gate dielectric profile

Abstract

A gate stack comprising a uniform thickness gate dielectric, a gate electrode, and an oxygen-diffusion-resistant gate cap is formed on a semiconductor substrate. Thermal oxidation is performed only on the drain side of the gate electrode, while the source side is protected from thermal oxidation. A thermal oxide on the drain side sidewall of the gate electrode is integrally formed with a graded thickness silicon oxide containing gate dielectric, of which the thickness monotonically increases from the source side to the drain side. The thickness profile may be self-aligned to the drain side edge of the gate electrode, or may have a portion with a self-limiting thickness. The graded thickness profile may be advantageously used to form a lateral diffusion metal oxide semiconductor field effect transistor providing an enhanced performance.