The invention discloses a process method of a shield gate trench type MOSFET. The method comprises the following steps 1, depositing a silicon oxide layer on a semiconductor substrate, and sequentially depositing a silicon nitride layer and a silicon oxide layer to form an ONO layer, and etching the ONO layer; 2, taking the ONO layer as a hard mask, and carrying out the downward etching of the semiconductor substrate, and forming a trench; 3, carrying out back etching on the ONO layer; 4, carrying out chamfer etching on the bottom of the formed groove; 5, depositing and forming a dielectric layer in the groove; step 6, depositing and filling a polycrystalline silicon layer in the trench; and 7, performing back etching on the deposited polycrystalline silicon layer. According to the processmethod disclosed by the invention, the back etching process of the ONO layer of the hard mask layer is added before a groove chamfer etching process, so that the morphology of the top of the groove is improved, and the process tolerance of polycrystalline silicon filling is increased; the groove etching angle is allowed to reach 88 degrees or above, after the groove etching angle is increased, the size of each device unit can be reduced, and the performance of the device can be enhanced.