Shield gate trench field effect transistor and preparation method thereof

Abstract

The invention provides a shield gate trench field effect transistor and a preparation method thereof. The method mainly comprises the steps: providing a substrate, forming an epitaxial layer on the upper surface of the substrate, forming a deep trench in the epitaxial layer, and forming a shielding oxide layer, shield polysilicon, a first isolation oxide layer and a second isolation oxide layer on the inner wall of the deep trench, wherein the density of the first isolation oxide layer is greater than that of the second isolation oxide layer; removing the second isolation oxide layer, a part of the first isolation oxide layer and the shielding oxide layer through wet etching, so that an obtuse angle is formed between the upper surface of the shielding oxide layer and the side wall of the deep trench; forming a gate oxide layer and gate polysilicon on the inner wall of the deep trench; and forming other structures of the field effect transistor. According to the method, the reverse voltage endurance capability of the gate oxide layer can be effectively improved, and other working parameters of the field effect transistor cannot be influenced; and the preparation method provided by the invention is easy to realize in process manufacturing and mass production.

Description

technical field [0001] The invention belongs to the field of design and manufacture of semiconductor devices, in particular to a shielded gate trench field effect transistor and a preparation method thereof. Background technique [0002] With the continuous development of semiconductor technology, the structure of metal oxide semiconductor field effect transistor (MOSFET) has also been continuously improved. Shielded gate trench field effect transistor (Trench Split Gate MOSFET) is one of the improved structures. Its main feature is to increase the shielded gate structure on the basis of traditional trench MOSFET to achieve better switching characteristics and higher source-to-drain strike. breakdown voltage, lower on-resistance and lower power consumption. Due to these advantages, trench shielded gate MOS devices are widely used in various power electronic systems. [0003] In the traditional power device structure, the gate withstand voltage of the MOS transistor is rela...

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Problems solved by technology

[0005] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a shielded gate trench field effect transistor and its preparation method, which is used to solve the problem of increasing the gate insulating layer of the shielded gate trench field effect transistor in the prior art. Thickness is used to improve the withstand voltage performance, but it will cause problems such as the reduction of other parameter characteristics when the field effect transistor is working.

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