Memory device and method of manufacturing the same

1. A method of manufacturing a memory device, the method comprising:

forming a first layer stack and a second layer stack at an interval on a foundation;

forming a first insulator that includes a first portion on a side surface of the first layer stack, a second portion on a side surface of the second layer stack, and a third portion on the foundation between the first layer stack and the second layer stack;

thinning part of the first portion of the first insulator and part of the second portion of the first insulator with an ion beam while leaving the third portion of the first insulator, before a material other than the first insulator is formed between the first layer stack and the second layer stack; and

forming a second insulator between the first portion of the first insulator and the second portion of the first insulator.

2. The method according to claim 1 , wherein:

the second insulator includes a first portion having a first surface and a second surface facing the first surface;

the first surface is in contact with the first portion of the first insulator; and

the second surface is in contact with the second portion of the first insulator.

3. The method according to claim 1 , wherein:

the forming of the second insulator includes filling an area between the first portion of the first insulator and the second portion of the first insulator with the second insulator.

4. The method according to claim 1 , wherein:

the first layer stack or the second layer stack includes an element that exhibits a magnetoresistive effect.

5. The method according to claim 4 , wherein:

the first layer stack or the second layer stack further includes a bidirectional switching element.

6. The method according to claim 1 , wherein:

the part of the first portion of the first insulator is a portion on an upper side of the first portion of the first insulator; and

the part of the second portion of the first insulator is a portion on an upper side of the second portion of the first insulator.

7. The method according to claim 1 , wherein:

the thinning of the first portion of the first insulator and the second portion of the first insulator includes emitting the ion beam at a first angle relative to a direction in which the side surface of the first layer stack or the side surface of the second layer stack extends.

8. The method according to claim 7 , wherein:

the first layer stack or the second layer stack further includes a bidirectional switching element.

9. The method according to claim 7 , wherein:

the first angle is θ;

θ

=

tan

-

1

⁡

(

L

-

2

⁢

T

s

-

bot

H

⁢

-

T

bot

)

where:

L is a length of the interval between the first layer stack and the second layer stack;

T s-bot is a thickness of the part of the first portion of the first insulator or the part of the second portion of the first insulator before being thinned;

H is a height of the first layer stack or the second layer stack; and

T bot is a thickness of the third portion of the first insulator.

10. The method according to claim 1 , wherein:

H/L> 1 is satisfied;

where:

H is a height of the first layer stack or the second layer stack; and

L is a length of the interval between the first layer stack and the second layer stack.

11. The method according to claim 1 , wherein:

the thinning of the part of the first portion of the first insulator and the second portion of the first insulator includes making the part of the first portion of the first insulator thin gradually toward a top of the first layer stack and making the part of the second portion of the first insulator thin gradually toward a top of the second layer stack.