Method of forming a trench gate MOSFET having a thick bottom oxide

摘要

A method of forming a trench gate MOSFET is provided. An epitaxial layer is formed on a substrate. A trench is formed in the epitaxial layer. A first insulating layer is conformally formed on surfaces of the epitaxial layer and the trench. A first conductive layer is formed at the bottom of the trench. A portion of the first insulating layer is removed to form a second insulating layer exposing an upper portion of the first conductive layer. An oxidation process is performed to oxidize the first conductive layer to a third insulating layer, wherein a fourth insulating layer is simultaneously formed on the surface of the epitaxial layer and on the sidewall of the trench. A second conductive layer is formed in the trench. Two body layers are formed in the epitaxial layer beside the trench. Two doped regions are formed in the body layers respectively beside the trench.

主权项

1. A method of forming a trench gate MOSFET, comprising:
forming an epitaxial layer with a first conductivity type on a substrate with the first conductivity type; forming a trench in the epitaxial layer; conformally forming a first insulating layer and a first conductive layer on surfaces of the epitaxial layer and the trench; filling up the trench with a second insulating layer; removing a portion of the first conductive layer to form a second conductive layer below the second insulating layer; removing the second insulating layer and a portion of the first insulating layer to form a third insulating layer below the second conductive layer; performing an oxidation process to oxidize the second conductive layer to a fourth insulating layer, wherein a fifth insulating layer is simultaneously formed on the surface of the epitaxial layer and on a sidewall of the trench by the oxidation process; forming a third conductive layer in the trench; forming two body layers with a second conductivity type in the epitaxial layer respectively beside the trench; and forming two doped regions with the first conductivity type in the body layers respectively beside the trench.