Three-dimensional memory device and method

1. A method comprising:

forming a word line between a pair of first dielectric layers;

depositing a data storage layer on sidewalls of the first dielectric layers and a sidewall of the word line;

depositing a channel layer on a sidewall of the data storage layer;

depositing a first dielectric layer on a sidewall of the channel layer;

forming a first isolation region on a sidewall of the first dielectric layer;

removing a first portion of the first isolation region, a second portion of the first isolation region remaining after the removing;

after removing the first portion of the first isolation region, patterning the first dielectric layer to form a back gate isolator; and

forming a bit line and a source line at opposing sides of the second portion of the first isolation region, the back gate isolator separating the channel layer from a first portion of the bit line and a second portion of the source line.

2. The method of claim 1 further comprising:

patterning the channel layer while patterning the first dielectric layer.

3. The method of claim 1 further comprising:

forming a second isolation region extending through the channel layer; and

patterning the channel layer while forming the second isolation region.

4. The method of claim 1 further comprising:

forming a second isolation region extending through the channel layer; and

patterning the channel layer after patterning the first dielectric layer and before forming the second isolation region.

5. The method of claim 1 , wherein the first dielectric layer is formed of aluminum oxide.

6. A method comprising:

forming a memory film on a sidewall of a word line;

forming a channel layer on a sidewall of the memory film;

forming a back gate layer on a sidewall of the channel layer;

forming an isolation region on a sidewall of the back gate layer;

after forming the isolation region, patterning the back gate layer to form a back gate isolator between the isolation region and the channel layer in a top-down view; and

forming a bit line and a source line at opposing sides of the isolation region in the top-down view, the back gate isolator disposed between the channel layer and a first extension portion of the bit line, the back gate isolator disposed between the channel layer and a second extension portion of the source line.

7. The method of claim 6 , wherein a first main portion of the bit line contacts the sidewall of the channel layer but not the sidewall of the memory film, and a second main portion of the source line contacts the sidewall of the channel layer but not the sidewall of the memory film.

8. The method of claim 6 , wherein a first main portion of the bit line contacts the sidewall of the channel layer and the sidewall of the memory film, and a second main portion of the source line contacts the sidewall of the channel layer and the sidewall of the memory film.

9. The method of claim 6 , wherein a first main portion of the bit line contacts the sidewall of the memory film but not the sidewall of the channel layer, and a second main portion of the source line contacts the sidewall of the memory film but not the sidewall of the channel layer.

10. The method of claim 6 , wherein the back gate layer is formed of aluminum oxide.

11. The method of claim 6 , wherein the isolation region, the first extension portion of the bit line, and the second extension portion of the source line have a same width in the top-down view.

12. The method of claim 6 , further comprising:

connecting a source line interconnect over and connected to the source line; and

forming a bit line interconnect over and connected to the bit line.

13. The method of claim 6 further comprising:

forming a staircase structure comprising the word line between a pair of dielectric layers.

14. A method comprising:

forming a channel layer on a sidewall of a memory film;

forming a back gate layer on a sidewall of the channel layer;

patterning the back gate layer to form a first back gate isolator and a second back gate isolator;

forming a sacrificial region between the first back gate isolator and the second back gate isolator in a top-down view;

dividing the sacrificial region into a first portion and a second portion by forming an isolation region between the first portion and the second portion of the sacrificial region in the top-down view; and

replacing the first portion and the second portion of the sacrificial region with, respectively, a bit line and a source line, the first back gate isolator disposed between the channel layer and the bit line, the second back gate isolator disposed between the channel layer and the source line.

15. The method of claim 14 , wherein the bit line is T-shaped in the top-down view and the source line is T-shaped in the top-down view.

16. The method of claim 14 , wherein the back gate layer is formed of aluminum oxide.

17. The method of claim 14 , further comprising:

forming a source line interconnect over and connected to the source line; and

forming a bit line interconnect over and connected to the bit line.

18. The method of claim 14 further comprising:

forming a staircase structure comprising a word line between a pair of dielectric layers; and

forming the memory film on a sidewall of the word line.

19. The method of claim 14 further comprising:

forming a second isolation region on a sidewall of the back gate layer; and

patterning the second isolation region, a first portion and a second portion of the second isolation region remaining after the patterning, the first back gate isolator disposed between the channel layer and the first portion of the second isolation region, the second back gate isolator disposed between the channel layer and the second portion of the second isolation region.

20. The method of claim 19 further comprising:

forming the sacrificial region between the first portion and the second portion of the second isolation region;

removing a portion of the sacrificial region by patterning the sacrificial region when patterning the back gate layer; and

redepositing material of the sacrificial region between the first portion and the second portion of the second isolation region.