Nonvolatile memory with resistance change layer

1. A nonvolatile memory device comprising:

a first conductive layer;

a second conductive layer;

a resistance change layer provided between the first conductive layer and the second conductive layer and having an electrical resistance configured to change with at least one of an applied electric field and a passed current, the resistance change layer having a lateral surface intersecting a plane perpendicular to a first direction from the first conductive layer toward the second conductive layer; and

a lateral layer contacting the lateral surface of the resistance change layer, a second direction from the lateral layer toward the lateral surface of the resistance change layer being parallel to the plane and the first lateral layer having an oxygen concentration higher than an oxygen concentration in the first resistance change layer,

the resistance change layer having a first portion, a second portion provided between the first portion and the second conductive layer, and a third portion provided between the first portion and the second portion, and

a length of the third portion along the second direction being longer than a length of the second portion along the second direction.

2. The device according to claim 1 , wherein the resistance change layer includes A α M β O γ , and the lateral layer includes A α1 M β1 O γ1 (γ1>γ), the A being a transition metal element, the M being a transition metal element, the O being oxygen.

3. The device according to claim 1 , wherein:

the first portion is disposed below the second portion in the first direction, and

a length of the first portion along the second direction is longer than the length of the third portion along the second direction.

4. The device according to claim 3 , wherein the resistance change layer includes A α M β O γ , and the lateral layer includes A α1 M β1 O γ1 (γ1>γ), the A being a transition metal element, the M being a transition metal element, the O being oxygen.

5. The device according to claim 3 , wherein the first conductive layer is an anode electrode.

6. The device according to claim 3 , wherein a side surface of the lateral layer is a curved surface.

7. The device according to claim 6 , wherein the lateral layer directly contacts to the first and second conductive layers.

8. The device according to claim 1 , wherein:

the first portion is disposed below the second portion in the first direction, and

a length of the third portion along the second direction is longer than the length of the first portion along the second direction.

9. The device according to claim 8 , wherein the resistance change layer includes A α M β O γ , and the lateral layer includes A α1 M β1 O γ1 (γ1>γ), the A being a transition metal element, the M being a transition metal element, the O being oxygen.

10. The device according to claim 8 , wherein a side surface of the lateral layer is a curved surface.

11. The device according to claim 10 , wherein the lateral layer directly contacts to the first and second conductive layers.

12. The device according to claim 1 , wherein at least part of the lateral layer is provided between the first conductive layer and the second conductive layer.

13. The device according to claim 1 , wherein:

the lateral layer includes a metal oxide having a substantially stoichiometric composition ratio, and

the resistance change layer includes the metal oxide with a proportion of oxygen reduced to 90% or less as compared with the first lateral layer.

14. The device according to claim 1 , wherein the resistance change layer and the lateral layer include an oxide of at least one selected from the group consisting of Si, Ti, Ta, Nb, Hf, Zr, W, Al, Ni, Co, Mn, Fe, Cu, and Mo.

15. The device according to claim 1 , wherein the first conductive layer and the second conductive layer include a material containing an element having a smaller absolute value of standard free energy of oxide formation than an element except oxygen contained in an oxide included in the first resistance change layer.

16. The device according to claim 1 , wherein the first conductive layer and the second conductive layer include at least one of W, Ta, Cu, TiN, TaN, WC, and highly doped silicon.

17. The device according to claim 1 , wherein a work function of the first conductive layer is different from a work function of the second conductive layer.