Semiconductor memory and method of manufacturing the same
View Patent ↗A semiconductor memory includes a plurality of stripe-like active areas formed by stacking, in a direction perpendicular to a substrate, a plurality of layers extending parallel to the substrate, a first gate electrode formed on first side surfaces of the active areas, the first side surfaces being perpendicular to the substrate, a second gate electrode formed on second side surfaces of the active areas, the second side surfaces being perpendicular to the substrate. The layers are patterned in self-alignment with each other, intersections of the active areas and the first gate electrode form a plurality of memory cells, and the plurality of memory cells in an intersecting plane share the first gate electrode.
1. A semiconductor memory device comprising:
a semiconductor substrate having a first part and a second part, the first part having a first upper surface, the second part having a second upper surface, a first distance between the first upper surface and an under surface of the semiconductor substrate being shorter than a second distance between the second upper surface and the under surface of the semiconductor substrate;
a plurality of layers arranged along a stacking direction perpendicular to the first upper surface and extending in a first direction parallel to the first upper surface, the plurality of layers having a first insulating layer disposed on the first upper surface, a first semiconductor layer disposed on a top surface of the first insulating layer, a second insulating layer disposed on a top surface of the first semiconductor layer, and a second semiconductor layer disposed on a top surface of the second insulating layer;
gate electrodes arranged along the first direction, each of the gate electrodes extending in the stacking direction;
first memory portions disposed, in a direction parallel to the first upper surface, between the gate electrodes and a side surface of the first semiconductor layer, the side surface being perpendicular to the first upper surface;
second memory portions disposed, in a direction parallel to the first upper surface, between the gate electrodes and a side surface of the second semiconductor layer, the side surface being perpendicular to the first upper surface; and
a peripheral circuit disposed on the second upper surface.
2. The device according to claim 1 , wherein:
a third distance between the second semiconductor layer and the under surface is shorter than the second distance.
3. The device according to claim 2 , wherein:
the second semiconductor layer is an uppermost layer of the semiconductor layers.
4. The device according to claim 1 , further comprising:
a first contact electrode electrically connected with the second semiconductor layer at a first contact surface,
wherein:
the peripheral circuit has a diffusion layer doped with an impurity and a second contact electrode electrically connected with the diffusion layer at a second contact surface, and
a fourth distance between the first contact surface and the under surface of the semiconductor substrate is longer than a fifth distance between the second contact surface and the under surface of the semiconductor substrate.
5. The device according to claim 4 , wherein:
the second semiconductor layer is an uppermost layer of the semiconductor layers.
6. The device according to claim 1 , wherein:
each of the gate electrodes extends in the stacking direction and has a third upper surface, a sixth distance between the third upper surface and the under surface of the semiconductor substrate being longer than the second distance.
7. The device according to claim 1 , wherein:
end portions of the semiconductor layers are electrically connected to a source contact electrode in common at a source contact surface, and
a seventh distance between the source contact surface and the under surface is shorter than the second distance.
8. The device according to claim 1 , wherein:
end portions of the semiconductor layers have a stair shape.
9. The device according to claim 1 , further comprising
a first contact electrode electrically connected with an end portion of the first semiconductor layer; and
a second contact electrode electrically connected with an end portion of the second semiconductor layer,
wherein:
an eighth distance between the end portion of the first semiconductor layer and the under surface is shorter than a ninth distance between the end portion of the second semiconductor layer and the under surface, and
the ninth distance is shorter than the second distance.
10. The device according to claim 1 , wherein:
the semiconductor substrate has a recess portion, the recess portion having the first upper surface and a side wall surface, and
a second insulating layer is disposed on the side wall surface.
11. The device according to claim 10 , wherein:
a shape of the side wall of each semiconductor layers has a curvature outward.
12. The device according to claim 1 , wherein:
each of the first memory portions and the second memory portions has a charge storage layer.
13. The device according to claim 1 wherein:
each of the first memory portions and the second memory portions has a chalcogenide layer.
14. The device according to claim 1 wherein:
each of the first memory portions and the second memory portions has a resistance change layer.