Semiconductor storage device and method of manufacturing semiconductor storage device
According to one embodiment, a semiconductor storage device includes a substrate, a first electric charge holder, and a channel layer. At least a part of the first electric charge holder is curved in a first cross section along a surface of the substrate. The channel layer is inside the first electric charge holder in the first cross section. At least a part of the channel layer is curved in the first cross section. The first electric charge holder has a curvature varying in accordance with a position in the first cross section. The channel layer has a film thickness varying in accordance with the curvature of the first electric charge holder in the first cross section.
1. A semiconductor storage device comprising:
a substrate;
a first electric charge holder, at least a part of the first electric charge holder being curved in a first cross section along a surface of the substrate;
a channel layer inside the first electric charge holder in the first cross section, at least a part of the channel layer being curved in the first cross section; and
a first conductor provided outside an entire circumference of the first electric charge holder in the first cross section,
wherein
the first electric charge holder has a curvature varying in accordance with a position in the first cross section,
the channel layer has a film thickness varying in accordance with the curvature of the first electric charge holder in the first cross section,
the first electric charge holder includes, in the first cross section, a first part and a second part, the second part having a larger curvature than the first part,
the channel layer includes, in the first cross section, a first part and a second part, the first part of the channel layer being alongside the first part of the first electric charge holder, the second part of the channel layer being alongside the second part of the first electric charge holder, and
the second part of the channel layer has a larger film thickness than the first part of the channel layer, and
a difference between film thicknesses at the first part and the second part of the channel layer is larger than a difference between film thicknesses at the first part and the second part of the first electric charge holder.
2. The semiconductor storage device according to claim 1 , wherein
the first part of the channel layer is alongside the first part of the first electric charge holder with a first insulating film sandwiched therebetween, and
the second part of the channel layer is alongside the second part of the first electric charge holder with the first insulating film sandwiched therebetween.
3. The semiconductor storage device according to claim 1 , wherein
a largest film thickness of the second part of the channel layer is larger than a smallest film thickness of the first part of the channel layer by 1 nm or more.
4. The semiconductor storage device according to claim 1 further comprising:
an insulator inside the channel layer, wherein
the insulator includes, in the first cross section, a first part and a second part, the first part of the insulator being alongside the first part of the first electric charge holder with the channel layer sandwiched therebetween, the second part of the insulator being alongside the second part of the first electric charge holder with the channel layer sandwiched therebetween, and
a difference between curvatures at the first part and the second part of the insulator is smaller than the difference between curvatures at the first part and the second part of the first electric charge holder.
5. The semiconductor storage device according to claim 4 , wherein
the first part of the insulator is alongside the first part of the first electric charge holder with the channel layer and a first insulating film sandwiched therebetween, and
the second part of the insulator is alongside the second part of the first electric charge holder with the channel layer and the first insulating film sandwiched therebetween.
6. The semiconductor storage device according to claim 1 , wherein
the channel layer has a ring shape, and the channel layer has an outer circumferential edge and an inner circumferential edge in the first cross section, and
the inner circumferential edge has a higher roundness than the outer circumferential edge.
7. The semiconductor storage device according to claim 1 , wherein
the channel layer has an oval ring shape in the first cross section, and the channel layer includes a first thick film portion at one end of the channel layer on a long axis of the oval ring shape, a second thick film portion at the other end of the channel layer on the long axis, a first thin film portion at the one end of the channel layer on a short axis of the oval ring shape orthogonal to the long axis, and a second thin film portion at the other end of the channel layer on the short axis,
the first thick film portion has a film thickness larger than each of the first thin film portion and the second thin film portion, and
the second thick film portion has a film thickness larger than each of the first thin film portion and the second thin film portion.
8. The semiconductor storage device according to claim 7 , wherein
the film thickness of the channel layer gradually increases as a position in the channel layer gets closer to the first thick film portion from the first thin film portion, gradually decreases as the position gets closer to the second thin film portion from the first thick film portion, gradually increases as the position gets closer to the second thick film portion from the second thin film portion, and gradually decreases as the position gets closer to the first thin film portion from the second thick film portion.
9. A semiconductor storage device comprising:
a substrate;
a first electric charge holder, at least a part of the first electric charge holder being curved in a first cross section along a surface of the substrate;
a channel layer inside the first electric charge holder in the first cross section, at least a part of the channel layer being curved in the first cross section; and
a first conductor provided outside the entire circumference of the first electric charge holder in the first cross section,
wherein
the first electric charge holder has a curvature varying in accordance with a position in the first cross section,
the channel layer has a film thickness varying in accordance with the curvature of the first electric charge holder in the first cross section, and
the film thickness of the channel layer varies at a rate of change higher than a rate of change in film thickness of the first electric charge holder in the first cross section.
10. The semiconductor storage device according to claim 9 further comprising:
an insulator inside the channel layer, wherein
the first electric charge holder includes, in the first cross section, a first part and a second part, the second part having a larger curvature than the first part,
the insulator includes, in the first cross section, a first part and a second part, the first part of the insulator being alongside the first part of the first electric charge holder with the channel layer sandwiched therebetween, the second part of the insulator being alongside the second part of the first electric charge holder with the channel layer sandwiched therebetween, and
a difference between curvatures at the first part and the second part of the insulator is smaller than the difference between curvatures at the first part and the second part of the first electric charge holder.
11. The semiconductor storage device according to claim 10 , wherein
the first part of the insulator is alongside the first part of the first electric charge holder with the channel layer and a first insulating film sandwiched therebetween, and
the second part of the insulator is alongside the second part of the first electric charge holder with the channel layer and the first insulating film sandwiched therebetween.
12. The semiconductor storage device according to claim 9 , wherein
the channel layer has a ring shape, and the channel layer has an outer circumferential edge and an inner circumferential edge in the first cross section, and
the inner circumferential edge has a higher roundness than the outer circumferential edge.
13. The semiconductor storage device according to claim 9 , wherein
the channel layer has an oval ring shape in the first cross section, and the channel layer includes a first thick film portion at one end of the channel layer on a long axis of the oval ring shape, a second thick film portion at the other end of the channel layer on the long axis, a first thin film portion at the one end of the channel layer on a short axis of the oval ring shape orthogonal to the long axis, and a second thin film portion at the other end of the channel layer on the short axis,
the first thick film portion has a film thickness larger than each of the first thin film portion and the second thin film portion, and
the second thick film portion has a film thickness larger than each of the first thin film portion and the second thin film portion.
14. The semiconductor storage device according to claim 13 , wherein
the film thickness of the channel layer gradually increases as a position in the channel layer gets closer to the first thick film portion from the first thin film portion, gradually decreases as the position gets closer to the second thin film portion from the first thick film portion, gradually increases as the position gets closer to the second thick film portion from the second thin film portion, and gradually decreases as the position gets closer to the first thin film portion from the second thick film portion.
15. A semiconductor storage device comprising:
a substrate;
a first electric charge holder, at least a part of the first electric charge holder being curved in a first cross section along a surface of the substrate;
a channel layer inside the first electric charge holder in the first cross section, at least a part of the channel layer being curved in the first cross section;
a first conductor provided outside the entire circumference of the first electric charge holder in the first cross section, and
a second electric charge holder at a position farther away from the substrate than the first electric charge holder, at least a part of the second electric charge holder being curved,
wherein
the first electric charge holder has a curvature varying in accordance with a position in the first cross section,
the channel layer has a film thickness varying in accordance with the curvature of the first electric charge holder in the first cross section, and
the first electric charge holder includes, in the first cross section, a first part and a second part, the second part having a larger curvature than the first part,
the second electric charge holder includes, in a second cross section, a first part and a second part, the second part of the second electric charge holder having a larger curvature than the first part of the second electric charge holder, the second cross section being along the surface of the substrate and farther away from the substrate than the first cross section,
the channel layer includes, in the first cross section, a first part and a second part, the first part of the channel layer being alongside the first part of the first electric charge holder, the second part of the channel layer being alongside the second part of the first electric charge holder, and the channel layer includes, in the second cross section, a third part and a fourth part, the third part of the channel layer being alongside the first part of the second electric charge holder, the fourth part of the channel layer being alongside the second part of the second electric charge holder, and
a difference between film thicknesses at the first part and the second part of the channel layer is larger than a difference between film thicknesses at the third part and the fourth part of the channel layer.
16. The semiconductor storage device according to claim 15 further comprising:
an insulator inside the channel layer, wherein
the first electric charge holder includes, in the first cross section, a first part and a second part, the second part having a larger curvature than the first part,
the insulator includes, in the first cross section, a first part and a second part, the first part of the insulator being alongside the first part of the first electric charge holder with the channel layer sandwiched therebetween, the second part of the insulator being alongside the second part of the first electric charge holder with the channel layer sandwiched therebetween, and
a difference between curvatures at the first part and the second part of the insulator is smaller than the difference between curvatures at the first part and the second part of the first electric charge holder.
17. The semiconductor storage device according to claim 16 , wherein
the first part of the insulator is alongside the first part of the first electric charge holder with the channel layer and a first insulating film sandwiched therebetween, and
the second part of the insulator is alongside the second part of the first electric charge holder with the channel layer and the first insulating film sandwiched therebetween.
18. The semiconductor storage device according to claim 15 , wherein
the channel layer has a ring shape, and the channel layer has an outer circumferential edge and an inner circumferential edge in the first cross section, and
the inner circumferential edge has a higher roundness than the outer circumferential edge.
19. The semiconductor storage device according to claim 15 , wherein
the channel layer has an oval ring shape in the first cross section, and the channel layer includes a first thick film portion at one end of the channel layer on a long axis of the oval ring shape, a second thick film portion at the other end of the channel layer on the long axis, a first thin film portion at the one end of the channel layer on a short axis of the oval ring shape orthogonal to the long axis, and a second thin film portion at the other end of the channel layer on the short axis,
the first thick film portion has a film thickness larger than each of the first thin film portion and the second thin film portion, and
the second thick film portion has a film thickness larger than each of the first thin film portion and the second thin film portion.
20. The semiconductor storage device according to claim 19 , wherein
the film thickness of the channel layer gradually increases as a position in the channel layer gets closer to the first thick film portion from the first thin film portion, gradually decreases as the position gets closer to the second thin film portion from the first thick film portion, gradually increases as the position gets closer to the second thick film portion from the second thin film portion, and gradually decreases as the position gets closer to the first thin film portion from the second thick film portion.