The invention discloses a silicon carbide Trench MOS device and a manufacturing method thereof, and belongs to the technical field of power semiconductors. The method includes: a layer of a polysilicon region distributed in a pi shape is additionally arranged under a trench gate structure of a conventional device, the polysilicon region and an epitaxial layer form a Si/SiC heterojunction, and a diode is integrated in the device. Compared with a parasitic silicon carbide diode which directly employs a silicon carbide Trench MOS, according to the silicon carbide Trench MOS device and the manufacturing method thereof, the junction voltage drop of the device diode during application is substantially reduced, and the switch-on characteristic of the device is improved through large junction area of the heterojunction; moreover, the gate-drain capacitance and the ratio of the gate-drain capacitance to the gate-source capacitance of the device are reduced, and the performance and the reliability of the device MOS during application are enhanced; besides, the silicon carbide Trench MOS device and the manufacturing method thereof are also advantageous in that the reverse recovery time is short, the reverse recovery charges are less, and advantages including low reverse leakage, high breakdown voltage, and good temperature stabilization performance of the conventional silicon carbide Trench MOS device are maintained. In conclusion, according to the silicon carbide Trench MOS device and the manufacturing method thereof, the prospect is wide in circuits such as inversion circuits and chopper circuits etc.