Manufacture method of false gate of back gate process

The invention provides a manufacture method of a false gate of a back gate process. The manufacture method includes the following steps: sequentially forming a false gate material layer and a hard mask material layer on a substrate, etching the hard mask material layer to form a hard mask pattern with wide top and narrow bottom, and utilizing the hard mask pattern as a mask to etch the false gate material layer in a dry method to form the false gate with wide top and narrow bottom. By means of the manufacture method of the false gate, the prior vertical false gate is manufactured into a regular trapezoid false gate with wide top and narrow bottom. After the false gate is removed, a regular trapezoid groove can be formed. Therefore, the manufacture method greatly facilitates filling of the following high-potassium or metal gate materials, expands a filling process window and improves device reliability accordingly.