The invention discloses a
semiconductor device and a preparation method thereof, the
semiconductor device comprises a substrate, an
active layer, a
trench gate, a source
electrode and a protection structure, the
active layer is arranged on one side of the substrate along the thickness direction, the
active layer comprises an epitaxial layer, a well region and a source region, the
trench gate is formed by extending from the surface, deviating from the substrate, of the epitaxial layer towards the substrate direction, and the protection structure is arranged on the surface of the
trench gate. The trench gate at least penetrates through the well region; the source
electrode is arranged on one side, opposite to the substrate, of the epitaxial layer, covers at least part of the source region and forms
ohmic contact; the protection structure is arranged on one side, opposite to the substrate, of the epitaxial layer, and an isolation
dielectric layer is arranged between the protection structure and the epitaxial layer; wherein the protection structure comprises a first doped region, a second doped region and a third doped region which are arranged along the direction far away from the source
electrode, the
conduction type of the first doped region is the same as that of the third doped region, the
conduction type of the first doped region is opposite to that of the second doped region, the first doped region and the source electrode form
ohmic contact, and the third doped region is electrically connected with the trench gate.