Convex shaped thin-film transistor device having elongated channel over insulating layer
View Patent ↗The present invention provides a semiconductor device that has a shorter distance between the bit lines and easily achieves higher storage capacity and density. The semiconductor device includes: first bit lines formed on a substrate; an insulating layer that is provided between the first bit lines and in a groove in the substrate, and has a higher upper face than the first bit lines; channel layers that are provided on both side faces of the insulating layer, and are coupled to the respective first bit lines; and charge storage layers that are provided on the opposite side faces of the channel layers from the side faces on which the insulating layers are formed.
1. A semiconductor device comprising:
a substrate, the substrate comprising a groove;
a plurality of first bit lines comprising a plurality of upper faces, the plurality of first bit lines provided on the substrate;
an insulating layer that is provided between the plurality of first bit lines on the substrate, the insulating layer comprising opposing side faces, wherein an upper face of the insulating layer is higher than a plurality of upper faces of the plurality of first bit lines; and
an ONO film comprising a top oxide film, a tunnel oxide film, and a plurality of charge storage layers, the top oxide film and the tunnel oxide film each comprising top, bottom and side surfaces,
wherein at least a portion of the bottom surface of the top oxide film is in direct contact with the top surface of the tunnel oxide film,
further wherein a path of a current flowing through the substrate and between the plurality of first bit lines is lengthened by the portion of the insulating layer provided in the groove of the substrate.
2. The semiconductor device as claimed in claim 1 , further comprising:
a plurality of channel layers provided on the side faces of the insulating layer and coupled to the respective first bit lines of the plurality of first bit lines; and
a plurality of charge storage layers provided between the side surfaces of the top oxide film and the tunnel oxide film.
3. The semiconductor device as claimed in claim 1 , wherein at least a portion of the insulating layer is provided in the groove of the substrate.
4. The semiconductor device as claimed in claim 1 , wherein the channel layers are coupled to each other on the insulating layer to form one channel layer.
5. The semiconductor device as claimed in claim 1 , further comprising
a second bit line that is provided on the insulating layer and is coupled to the plurality of channel layers.
6. The semiconductor device as claimed in claim 5 , wherein two charge storage layers of the plurality of charge storage layers are formed at a portion of the ONO film between a first bit line and a second bit line.
7. The semiconductor device as claimed in claim 1 , wherein a pair of charge storage layers of the plurality of charge storage layers are physically separated by the top surface of the tunnel oxide film.
8. The semiconductor device as claimed in claim 1 , wherein the plurality of channel layers comprises a plurality of polysilicon layers.
9. The semiconductor device as claimed in claim 1 , wherein the plurality of charge storage layers comprises a plurality of silicon nitride films.
10. The semiconductor device as claimed in claim 1 , further comprising a plurality of word lines perpendicular to the plurality of first bit lines, the insulating film being interposed between the plurality of word lines and the plurality of charge storage layers.
11. The semiconductor device as claimed in claim 10 , wherein at least a portion of the plurality of word lines comprises a gate.
12. The semiconductor device as claimed in claim 10 , further comprising:
an interlayer insulating film;
a plurality of wiring layers; and
a protection film,
wherein the interlayer insulating film, the plurality of wiring layers, and the protection film are provided over the plurality of word lines.
13. The semiconductor device as claimed in claim 12 , wherein the semiconductor device comprises a flash memory device.
14. The semiconductor device as claimed in claim 1 , wherein the plurality of charge storage layers comprises a plurality of floating gates.
15. The semiconductor device as claimed in claim 1 , wherein the plurality of charge storage layers are formed on the side faces of the insulating layer according to a sidewall technique.
16. The semiconductor device as claimed in claim 1 , wherein the plurality of charge storage layers are formed by isolating two portions of a single contiguous charge storage layer from each other via etching.
17. The semiconductor device as claimed in claim 1 , wherein the charge storage layers of the plurality of charge storage layers are physically separated by the top surface of the tunnel oxide.
18. The semiconductor device as claimed in claim 1 , wherein the insulating layer comprises side faces oblique with respect to a surface of the substrate.
19. The semiconductor device as claimed in claim 1 , wherein a punch through condition is prevented by the portion of the insulating layer provided in the groove of the substrate.