Trench MOSFET and manufacturing method thereof

Abstract

The invention discloses a trench metal oxide semiconductor field effect transistor (MOSFET). The structure comprises a primitive cell region and a peripheral region, wherein a device unit structure ofa trench MOSFET is formed in the primitive cell region, a trench MOS capacitor used for reducing the nonlinearity of the output capacitance of the trench MOSFET is formed in the peripheral region, and the trench MOS capacitor comprises a second trench gate formed by superposing a second gate dielectric layer and a second polysilicon gate which are formed in a second trench; a source region is notformed on the surface of the first epitaxial layer covered on the side surface of the second polysilicon gate, a drift region formed by the first epitaxial layer extends into the whole primitive cellregion and the peripheral region, and a drain region is formed on the back surface of the drift region; the top of the second polysilicon gate is connected to the source electrode through a contact hole; the trench MOS capacitor and the device unit structure form a parallel structure, and the output capacitance of the whole trench MOSFET is improved and the nonlinearity of the output capacitanceis reduced when the device is reversely biased. The invention further discloses a manufacturing method of the trench MOSFET.

Description

technical field [0001] The invention relates to the field of manufacturing semiconductor integrated circuits, in particular to a trench MOSFET; the invention also relates to a method for manufacturing the trench MOSFET. Background technique [0002] Such as figure 1 As shown, it is a structural schematic diagram of the device unit structure of the existing trench MOSFET. The existing trench MOSFET is formed by connecting multiple device unit structures in parallel. Each of the device unit structures includes: [0003] The first trench gate is formed by stacking the first gate dielectric layer 8 and the first polysilicon gate 9 formed in the first trench. [0004] The drift region 2 is composed of the first epitaxial layer 2 doped with the first conductivity type. [0005] The body region 3 is composed of a doped region of the second conductivity type formed on the surface of the drift region 2 . [0006] The source region 4 is composed of a heavily doped region of the fir...

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Problems solved by technology

like figure 2 Shown is the output capacitance curve of the existing trench MOSFET; where curve 101 is the output capacitance curve of the existing trench MOSFET, the abscissa of the output capacitance curve is the drain voltage, the ordinate is the normalized capacitance, and the normalized Capacitor 1 has a capacitance of 1 when the drain voltage is 0V. It can be seen that the output capacitance at 40V is 20% of that at 0V. When the drain voltage increases from 0V to 40V, the output capacitance is less than 1 / 5, so the input capacitance of existing devices drops sharply with increasing drain voltage

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