The invention provides a
semiconductor device with a
trench gate and a forming method thereof, and the method comprises the steps: firstly executing a first
exposure process and a first
etching process to form a
bottom gate oxide of a trench, then forming a
monocrystalline silicon layer, executing a second
exposure process and a second
etching process to form a trench, exposing the top surface of the
bottom gate oxide through the trench, and then forming the
trench gate, the
trench gate is located in the trench and located on the
bottom gate oxide, the first
exposure process and the second exposure process adopt the same
mask, and the polarity of the second
photoresist layer is opposite to that of the first
photoresist layer. The unexpected effects of the invention are that the thickness of the bottom
gate oxide of the groove can be more conveniently controlled, the bottom
gate oxide of the groove is firstly formed, and then the
monocrystalline silicon layer and the groove are formed, so that the problem that the bottom
gate oxide is easy to seal in advance due to a high-density
plasma process after the groove is formed is avoided, the process difficulty can be simplified, and the production efficiency is improved. And meanwhile, the possibility of thick bottom gate oxide is provided for the MOS device with a small critical size, and the density of the device can be improved.