Semiconductor device and method for manufacturing the same

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

• forming a stacked body by alternately stacking first insulating layers and second insulating layers above a substrate;
• processing at least one side of the stacked body in a staircase pattern to form a staircase portion such that the second insulating layer remains on a tread surface of each stair;
• partially removing the second insulating layer situated in a corner between a riser of the staircase portion and the tread surface of a stair under the riser;
• forming a third insulating layer on the staircase portion;
• substituting the second insulating layer situated under the first insulating layer with a conductive layer while causing the second insulating layer remaining on the tread surface portion to remain;
• and
• forming contacts penetrating the third insulating layer, the second insulating layer, and the first insulating layer on the staircase portion and leading from an upper surface of the third insulating layer to the conductive layer under the first insulating layer,
• forming a gap between the second insulating layer and the conductive layer on the same first insulating layer, and
• providing, on the same first insulating layer, the third insulating layer in the gap between the second insulating layer and the conductive layer.