The invention discloses a preparation method of a
trench gate in a trench MOS device. The preparation method of the
trench gate in the trench MOS device is characterized in that the thickness of a gate oxidation film at the bottom of a trench is larger than the thickness of a gate oxidation film at the sidewall of the trench. The preparation method includes the following steps that: 1, a trench is formed on a
silicon wafer through photo-
etching and
etching, and a
trench gate is required to be produced on the
silicon wafer; 2, a first gate oxidation film is grown; 3,
spin coating of
photoresist is performed; 4, the
photoresist is removed partially, and part of the
photoresist, which is located at the bottom of the trench, is reserved; 5, a part of the first gate oxidation film, which is located at the sidewall of the trench and the surface of the
silicon wafer, is removed, and a part of the first gate oxidation film, which is located at the bottom of the trench, is reserved, and part of the photoresist, which is located at the bottom of the trench, is removed; 6, a second gate oxidation film is grown;
polycrystalline silicon is filled; 8, planarization is performed on the
polycrystalline silicon through etch-back or chemical mechanical lapping, and the final trench gate can be formed. With the preparation method of the trench gate in the trench MOS device of the invention adopted,
parasitic capacitance between a gate and a drain can be reduced, and the switching speed of the trench MOS device can be improved, and switching loss can be decreased, and at the same time, the problem of proneness to
electric breakdown at the bottom of the trench of the trench MOS device can be solved.