Preparation method of split gate MOSFET device and split gate MOSFET device

Abstract

The invention relates to the technical field of semiconductors, in particular to a preparation method of a split gate MOSFET device and the split gate MOSFET device. The method comprises the steps of:S1, providing a substrate, forming an epitaxial layer on the substrate, and enabling the width of the bottom surface of the epitaxial layer to be equal to the width of the top surface of the substrate; wherein the corresponding resistivity of the epitaxial layer is changed in a non-uniform gradual change manner from bottom to top. The preparation method has the beneficial effects that: the epitaxial layer is formed on the substrate, and the corresponding resistivity of the epitaxial layer from bottom to top is changed in a non-uniform gradual change manner, so that the internal electric fielddistribution of the device is optimized, the coverage area of two-dimensional breakdown electric field lines at the same position of the device with the same size is larger, and while the electric field intensity is improved, the intensity of the electric field close to the substrate direction is obviously increased, and a depletion region is broadened downwards, so that the breakdown voltage isimproved, and the on-resistance and the static loss of the device are reduced under the same target voltage.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for preparing a split-gate MOSFET device and the split-gate MOSFET device. Background technique [0002] The split gate MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor metal-oxide semiconductor field effect transistor) power device is an improved trench power MOSFET based on the traditional trench U-MOSFET, and its switching speed Faster, lower switching losses, and better device performance. [0003] The traditional trench U-MOSFET has only one layer of polysilicon in the deep trench, while the split gate MOSFET adopts a charge-coupled structure, that is, the deep trench of the split gate MOSFET has two layers of polysilicon, the upper polysilicon is the gate polysilicon, and the lower polysilicon For the source polysilicon, on the one hand, the split gate acts as a polycrystalline field plate in the body to assist in depleting the drift region, thereb...

AI Technical Summary

Problems solved by technology

However, whether it is a single-layer split-gate MOSFET or a double-layer split-gate MOSFET, its resistivity is constant, which cannot meet the needs of practical applications.

Therefore, it has become a difficult problem for those skilled in the art to solve the problem that the above-mentioned split-gate MOSFET has a constant resistivity and cannot meet the needs of practical applications.

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