Semiconductor memory device and method for manufacturing semiconductor memory device

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

• forming a stacked body in which a plurality of first sacrificial layers and a plurality of first insulating layers are alternately stacked;
• processing a terrace portion of each of the plurality of first sacrificial layers in a staircase shape to form a staircase portion of the stacked body;
• thinning the terrace portion of each of the plurality of first sacrificial layers;
• forming a pillar that penetrates the stacked body at a position away from the staircase portion in a first direction intersecting a stacking direction of the stacked body;
• forming a contact hole that penetrates the terrace portion of one first sacrificial layer among the plurality of first sacrificial layers and lower first sacrificial layers below the one first sacrificial layer in the staircase portion;
• retreating the one first sacrificial layer and the lower first sacrificial layers, which are exposed to a side wall of the contact hole, from the side wall to form a first flange portion that protrudes toward the one first sacrificial layer on the side wall of the contact hole at a height position of the one first sacrificial layer and to form a plurality of second flange portions that protrude toward the lower first sacrificial layers on the side wall of the contact hole at height positions of the lower first sacrificial layers;
• filling each of the plurality of second flange portions with a second insulating layer;
• replacing each of the plurality of first sacrificial layers with a conductive material to form one first conductive layer from the one first sacrificial layer and to form lower first conductive layers from the lower first sacrificial layers;
• and
• filling the contact hole and the first flange portion with a second conductive layer to form a contact connected to the one first conductive layer in the terrace portion of the one first conductive layer.