The invention provides a trench MOSFET (Metal Oxide Semiconductor Field Effect Transistor) device and a manufacturing method thereof. The device comprises an N-type heavily doped substrate and an N-type lightly doped epitaxial layer which is formed on the N-type heavily doped substrate, wherein a plurality of cellular area trench structures and a plurality of terminal area trench structures are formed in the N-type lightly doped epitaxial layer; the depth of the terminal area trench structures is greater than the depth of the cellular area trench structures. Since an inversion layer is formed on the surface of a trench gate when the device is in work, the length of the inversion layer can be lengthened by the deeper terminal area trench structures, the depletion degree around the terminal area trench structures is higher; thus the voltage endurance capability of a medium pressure MOSFET terminal area is favorably improved.