Pi-type trench gate silicon carbide MOSFET device and preparation method thereof

The invention discloses a pi-type trench gate silicon carbide MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) device and a preparation method thereof, relates to a power semiconductor device, and aims to protect a trench gate oxide layer under the condition of not increasing the channel resistance and the process complexity of the device. A first trench gate and a second trench gate which are shallower than the second conductive type heavily doped deep well region in depth are arranged on the left side wall and the right side wall of the second conductive type heavily doped deep well region respectively, and interlayer dielectric layers are arranged on the top of the first trench gate and the top of the second trench gate respectively. The first conductive type heavily doped source electrode region is arranged in the first trench gate, the interlayer dielectric layer extends outwards to cover a part of the first conductive type heavily doped source electrode region, and the first trench gate and th