The invention relates to the technical field of semiconductors, particularly to a trench field effect transistor and manufacturing method thereof. The trench field effect transistor manufactured by the invention includes a substrate, an n- epitaxial layer, a p type body region, n+ active regions, a trench and a polycrystalline silicon gate and a gate oxide layer which are arranged in the trench, the trench also contains an insulating medium layer, the insulating medium layer segments one side of the polycrystalline silicon gate which is close to the bottom of the trench into two parts which are close to the p type body region at two sides separately, and a p type doping region is formed between the trench bottom corresponding to one side of the polycrystalline silicon gate close to the trench bottom and the n- epitaxial layer. The trench field effect transistor provided by the invention effectively reduces gate-drain parasitic capacitance, and improves switching speed.