Groove MOSFET device and preparation method thereof

The invention relates to the technical field of semiconductors, and particularly discloses a trench MOSFET device and a preparation method thereof, the device comprises an N-type substrate, the N-type substrate is sequentially provided with an N-type epitaxy and two Pwell regions from bottom to top, and the two Pwell regions are respectively located at two sides of the top of the N-type epitaxy; an N + region and a first P + region are arranged in the Pwell region, and the N + region and the first P + region are located at the top of the Pwell region; two inverted trapezoidal grooves are also arranged between the two Pwell regions, and one bevel edge of each inverted trapezoidal groove is in contact with the corresponding Pwell region and N + region; a gate oxide layer is deposited in the inverted trapezoidal groove; a polycrystalline silicon gate region is also arranged in the inverted trapezoidal groove, and the polycrystalline silicon gate region is close to the corresponding Pwell region and N + region; a