Semiconductor power device and preparation method thereof

The invention provides a semiconductor power device and a preparation method thereof, and the semiconductor power device comprises a protection unit which is located in a drift layer and comprises a first epitaxial protection layer which surrounds the side wall and the bottom surface of a gate structure; the second doped protection layer is located on the side, facing the semiconductor substrate layer, of the first epitaxial protection layer and makes contact with the first epitaxial protection layer, the conduction type of the second doped protection layer is opposite to that of the first epitaxial protection layer, and the second doped protection layer and the first epitaxial protection layer form a PN junction; and the channel region is positioned in the first epitaxial protection layer on the side wall of the gate structure. The electric field concentration of a bottom region of a gate structure of the semiconductor power device in a reverse blocking state is improved, the doping concentration and length