Trench MOSFET device with improved on-resistance

Abstract

A trench MOSFET device comprises: a substrate 200 of a first conductivity type, an epitaxial layer of the first conductivity type wherein the epitaxial layer has a lower impurity concentration than the substrate, a trench extending into the epitaxial layer, an insulated conductive region 211 within the trench, a doped region 206 of the first conductivity type formed within the epitaxial layer between a bottom portion of the trench and the substrate, wherein the doped region has an impurity concentration that is lower than that of the substrate and higher than that of the epitaxial layer, a body region 204 of a second conductivity type formed within an upper portion of the epitaxial layer and adjacent trench wherein the body region extends to a lesser depth from the upper surface of the epitaxial layer than does the trench and a source region 212 within the body region.

Description

technical field [0001] The present invention relates to trench MOSFET devices, and more particularly to trench MOSFET devices with increased on-resistance. Background technique [0002] A trench MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a transistor in which a channel is formed vertically and a gate is formed in a trench extending between source and drain regions. A trench lined with a thin insulating layer such as an oxide layer and filled with a conductor such as polysilicon (ie, polycrystalline silicon) allows for less compressive current flow, and thus provides lower specific on-resistance values. Examples of trench MOSFET transistors are disclosed, for example, in US Pat. Nos. 5,072,266, 5,541,425, and 5,866,931, which are incorporated herein by reference. [0003] As a specific example, figure 1 A half hexagonal trench MOSFET structure 21 disclosed in US Pat. No. 5,072,266 is illustrated. The structure includes an n+ substrate 23 on which a prede...

AI Technical Summary

Problems solved by technology

However, as a known technique, when the epitaxial layer becomes thinner, the risk of breakdown increases, especially in the termination region which is more susceptible to breakdown

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