A method and a 3D memory device for manufacturing a semiconductor device are disclosed. The method comprises the following steps of: forming an insulating stack structure on a semiconductor substrate,including alternately stacking a first interlayer insulating layer and a second interlayer insulating layer; Forming an isolation structure through the insulating laminate structure; Replacing the first interlayer insulating layer on one side of the isolation structure with a gate conductor to form a first gate stack structure; And replacing the second interlayer insulating layer on the other side of the isolation structure with a gate conductor, forming a second gate stack structure, wherein the first isolation structure separates the first gate stack structure from the second gate stack structure, and gate conductors of the first gate stack structure and gate conductors of the second gate stack structure are staggered in a direction perpendicular to a surface of the semiconductor substrate. By staggered the gate conductors of the first gate stack structure and the gate conductors of the second gate stack structure, the memory density of the semiconductor device is increased and thespace utilization ratio of the semiconductor device is improved.