MOSFET and preparation method thereof

Abstract

The invention relates to a preparation method of a MOSFET. 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 by taking the gate isolation walls as mask layers so as to form a first trench in the source-drain area of the substrate; forming second isolation walls at the side wall of the first trench and the two sides of the gate isolation walls; performing isotropy etching on the semiconductor substrate by taking the second isolation walls as mask layers so as to form a second trench; selectively epitaxially growing an epitaxial layer on the surface of the second trench, at the same time of epitaxy, performing an original position doping with a type opposite from the type of a source drain; etching and removing the second isolation walls; selectively epitaxially growing the source drain, at the same time of the epitaxy, performing original position doping; and forming third isolation walls at the two sides of the gate isolation walls. By using the method, the problem of transverse diffusion of source / drain in the prior art can be eliminated, and the source drain series resistance can be reduced.

Description

technical field [0001] The invention relates to the field of semiconductor device preparation, in particular, the invention relates to a MOSFET device 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 is widely used in large-scale integrated circuits (Large-Scale Integrated Circuits, LSI) or ultra-large It is widely used in the field of integrated circuits (Very Large-Scale Integrated Circuits, VLSI). [0003] With the increasing progress of the manufacturing process of semiconductor integrated circuits, in the past few decades, in order to obt...

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