A kind of mosfet and preparation method thereof

Abstract

The invention relates to a MOSFET and a preparation method thereof. The method comprises: providing a semiconductor substrate, the semiconductor substrate having shallow trench isolation formed therein; forming a gate structure on the semiconductor substrate; forming gate isolation walls at the two sides of the gate structure; etching the substrate so as to form a first trench in the source-drain area of the substrate; forming second isolation walls at the two sides of the gate isolation walls; etching the semiconductor substrate by taking the second isolation walls as mask layers so as to form a second trench; epitaxial growing a sacrifice material layer on the surface of the second trench; etching and removing the second isolation walls; epitaxial growing a silicon material layer and forming third isolation walls at the two sides of the gate isolation walls; etching the shallow trench isolation so as to expose the sacrifice material layer; etching and removing the sacrifice material layer; and depositing a growth interlayer dielectric layer and flattening same, and forming an air buried layer at a side surface relative to the source-drain area. By using the MOSFET and the method, short channel effects and parasitic capacitance can be better eliminated.

Description

technical field [0001] The invention relates to the field of transistor preparation, in particular, the invention relates to a MOSFET and a preparation method thereof. Background technique [0002] Metal-Oxide-Semiconductor-Field-Effect Transistor (MOSFET) is a field-effect transistor that can be used in analog circuits and digital circuits. A typical MOSFET device includes a gate, a source, and a drain. The source and drain are close to the gate. The very bottom region is also formed with a lightly doped region (LDD region). Due to the advantages of low manufacturing cost, small use area, and high integration, it can be used in large-scale integrated circuits (Large-Scale Integrated Circuits, LSI) or ultra-large integrated circuits. Circuits (VeryLarge-ScaleIntegratedCircuits, VLSI) are widely used in the field. [0003] With the increasing progress of the manufacturing process of semiconductor integrated circuits, in the past few decades, in order to obtain better circuit...

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Problems solved by technology

[0009] In order to solve the problems in the prior art that thermal oxidation buried oxygen is introduced into too much heat budget in the process of MOSFET preparation, and the prepared device has relatively large short channel effect and parasitic capacitance, the present invention improves the existing preparation method and adopts air as insulation Dielectric to further reduce source-drain parasitic capacitance

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