Semiconductor storage device comprising staircase portion

A semiconductor storage device according to an embodiment includes: a stacked body in which a plurality of conductive layers are stacked via an insulating layer and which has a memory region in which a plurality of memory cells are disposed and a staircase region in which end portions of the plurality of conductive layers form a staircase shape. A first region of the staircase region includes a first sub-staircase portion ascending in a first direction toward the memory portion, and a second sub-staircase portion disposed side by side with the first sub-staircase portion in a second direction opposite to the first direction from the first sub-staircase portion and ascending in the second direction.