Three-dimensional memory devices and fabricating methods thereof

1. A method for forming a three-dimensional (3D) NAND memory device, comprising:

forming a plurality of hybrid shallow trench isolation structures in a substrate, comprising:

forming at least one row of shallow trenches extending in the horizontal direction in the substrate,

forming the plurality of hybrid shallow trench isolation structures in the at least one row of shallow trenches,

forming a dielectric sublayer in the at least one row of shallow trenches,

removing an upper portion of the dielectric sublayer, and

forming a conductive sublayer on the remaining portion of the dielectric sublayer and in the at least one row of shallow trenches;

forming an alternating dielectric stack on the substrate, the alternating dielectric stack including a plurality of dielectric layer pairs each comprising a first dielectric layer and a second dielectric layer different from the first dielectric layer;

forming a plurality of channel structures in the alternating dielectric stack;

forming a slit penetrating vertically through the alternating dielectric stack and extending in a horizontal direction to divide the plurality of channel structures and to expose a row of hybrid shallow trench isolation structures;

replacing the second dielectric layers in the alternating dielectric stack with a plurality of gate structures through the slit;

forming a spacer wall to fill the slit; and

forming a plurality of array common source contacts each in electric contact with a corresponding hybrid shallow trench isolation structure of the plurality of hybrid shallow trench isolation structures, comprising:

forming a plurality of via holes each vertically penetrating the substrate and the dielectric sublayer of a corresponding hybrid shallow trench isolation structure of the plurality of hybrid shallow trench isolation structures, and

forming the plurality of array common source contacts in the plurality of via holes respectively,

each array common source contact being in electrical contact with the conductive sublayer of the corresponding shallow trench isolation structure.

2. The method of claim 1 , wherein forming the plurality of hybrid shallow trench isolation structures comprises:

forming the plurality of hybrid shallow trench isolation structures arranged in an array, the array including a plurality rows of hybrid shallow trench isolation structures extending paralleling in the horizontal direction.

3. The method of claim 2 , wherein forming the slit comprises:

forming a plurality of slits each expose a corresponding row of shallow trench isolation structures.

4. The method of claim 1 , wherein forming the plurality of channel structures comprises:

forming a channel hole extending vertically through the alternating dielectric stack;

forming an epitaxial layer in a bottom portion of the channel hole;

forming a functional layer on a sidewall of the channel hole;

forming a channel layer covering a sidewall of the functional layer;

forming a filling structure to fill the channel hole; and

forming a channel plug in a top portion of the channel hole.

5. The method of claim 4 , wherein forming the functional layer comprises:

forming a barrier layer on a sidewall of the channel hole configured to block an outflow of the electronic charges during operation;

forming a storage layer on a surface of the barrier layer configured to store electronic charges during operation; and

forming a tunneling layer on a surface of the storage layer configured to tunnel electronic charges during operation.

6. The method of claim 1 , wherein forming the plurality of array common source contacts comprises:

forming a plurality of through holes vertically penetrating the spacer wall, each expose the conductive sublayer of a corresponding shallow trench isolation structure; and

forming the plurality of array common source contacts in the plurality of through holes respectively, each array common source contact being in electrical contact with the conductive sublayer of the corresponding shallow trench isolation structure.

7. The method of claim 6 , further comprising:

forming a staircase structure including a plurality of staircases each comprising a conductive surface; and

forming a plurality of word line contacts simultaneously with the formation of the plurality of array common source contacts, each word line contacts being in electrical contact with the conductive surface of the corresponding staircase.

8. The method of claim 6 , further comprising:

forming a transistor of a peripheral device in the substrate; and

forming a peripheral contact simultaneously with the formation of the plurality of array common source contacts, the peripheral contact being in electrical contact with the transistor.

9. A three-dimensional (3D) NAND memory device, comprises:

a substrate including a plurality of hybrid shallow trench isolation structures, each hybrid shallow trench isolation structure comprising a dielectric sublayer and a conductive sublayer both embedded in the substrate;

an alternating dielectric/conductive stack including a plurality of dielectric/conductive layer pairs on a substrate, each of the plurality of dielectric/conductive layer pairs comprising a dielectric layer and a conductive layer;

a plurality of channel structures vertically penetrating the alternating dielectric/conductive stack;

a slit penetrating vertically through the alternating dielectric/conductive stack and extending between the plurality of channel structures in a horizontal direction;

a spacer wall in the slit; and

a plurality of array common source contacts each in electric contact with a corresponding hybrid shallow trench isolation structure of the plurality of hybrid shallow trench isolation structures,

each array common source contact being in electrical contact with the conductive sublayer of the corresponding shallow trench isolation structure.

10. The device of claim 9 , wherein:

the plurality of hybrid shallow trench isolation structures are arranged in an array, the array including a plurality rows of hybrid shallow trench isolation structures extending paralleling in the horizontal direction; and

the plurality of array common source contacts are arranged in the array, each array common source contact being in electric contact with a corresponding one of the plurality of hybrid shallow trench isolation structures.

11. The device of claim 9 , wherein the plurality of channel structures comprises:

a channel hole extending vertically through the alternating dielectric/conductive stack;

an epitaxial layer in a bottom portion of the channel hole;

a functional layer on a sidewall of the channel hole;

a channel layer covering a sidewall of the functional layer;

a filling structure filling the channel hole; and

a channel plug in a top portion of the channel hole.

12. The device of claim 11 , wherein the functional layer comprises:

a barrier layer on a sidewall of the channel hole configured to block an outflow of the electronic charges during operation;

a storage layer on a surface of the barrier layer configured to store electronic charges during operation; and

a tunneling layer on a surface of the storage layer configured to tunnel electronic charges during operation.

13. The device of claim 9 , wherein the plurality of array common source contacts are vertically penetrating the spacer wall.

14. The device of claim 13 , further comprising:

a staircase structure including a plurality of staircases each comprising a conductive surface; and

a plurality of word line contacts each being in electrical contact with the conductive surface of the corresponding staircase;

wherein the plurality of word line contacts and the plurality of array common source contacts are formed simultaneously in a single process.

15. The device of claim 13 , further comprising:

a transistor of a peripheral device in the substrate; and

a peripheral contact being in electrical contact with the transistor;

wherein the peripheral contact and the plurality of array common source contacts are formed simultaneously in a single process.

16. The device of claim 9 , wherein each of the plurality of array common source contacts is vertically penetrating the substrate and the dielectric sublayer of a corresponding shallow trench isolation structure.