Semiconductor device and manufacturing method thereof

The invention provides a semiconductor device and a manufacturing method thereof, and the method comprises the steps: forming a semiconductor structure which comprises a substrate, a stacking structure and a hard mask layer, and the stacking structure and the hard mask layer are sequentially formed in the longitudinal direction perpendicular to the substrate; a patterned photoresist layer is formed on the hard mask layer, the photoresist layer is provided with at least one first opening, and the first opening comprises a first part opening, a middle part opening and a second part opening which are sequentially distributed in the first direction, the first partial opening, the middle partial opening and the second partial opening respectively have a first width, a middle width and a second width in the second direction, and the middle width is smaller than the first width and the second width. By forming the first opening with the small-size middle part opening, the distribution of the polymer when the first g