Three-dimensional semiconductor memory device including slit with lateral surfaces having periodicity

A manufacturing method of a semiconductor device, the method comprising:

• forming a stacked body including N-number of layers (N is an integer of 2 or more) above a semiconductor substrate;
• stacking an upper layer film above the stacked body;
• forming first opening portions penetrating the stacked body and the upper layer film in a stacking directions;
• embedding columnar bodies respectively into the first opening portions;
• reducing a film thickness of the upper layer film such that upper ends of the columnar bodies protrude above the stacked body;
• forming a mask layer on the upper layer film such that protruding portions of the columnar bodies are covered with the mask layer;
• forming a second opening portion in the mask layer, while leaving the mask layer on sidewalls of the upper ends of the columnar bodies, such that the upper layer film is exposed from the mask layer by the second opening portion;
• and
• etching the upper layer film and M-number of layers (M is an integer of 1 or more and (N−2) or less) of the stacked body from above through the second opening portion,
• wherein the stacked body includes first insulators and second insulators, which are different from each other in etching rate and are alternately stacked.