Inductor

1. An inductor comprising:

a first conductor spirally extending in a plane;

a second conductor spirally extending in a plane, wherein the second conductor is stacked on and joined to the first conductor;

an insulation film covering a surface of the first conductor and a surface of the second conductor; and

a magnetic body covering a surface of the insulation film and embedding the first conductor and the second conductor,

wherein the first conductor and the second conductor are connected to form a helical coil,

wherein the first conductor includes an inner circumferential end, an outer circumferential end, and a conductor portion spirally extending from the inner circumferential end toward the outer circumferential end,

wherein the inner circumferential end includes a projection projecting toward the second conductor and joined to the second conductor,

wherein the projection is tapered to have a width that gradually decreases in a direction in which the projection projects toward the second conductor, and

wherein the inner circumferential end except the projection, the outer circumferential end, and the conductor portion are reversely tapered to have a width that gradually increases in the direction in which the projection projects toward the second conductor.

2. The inductor according to claim 1 , wherein the projection is joined to the second conductor by diffusion bonding or a conductive bonding material.

3. The inductor according to claim 1 , wherein the first conductor includes a first surface facing the second conductor, wherein the projection is formed on the first surface, and a second surface opposite to the first surface, and a planar shape of the first surface has a greater dimension than a planar shape of the second surface.

4. The inductor according to claim 1 , further comprising:

a first plating film formed on a surface of the first conductor; and

a second plating film formed on a surface of the second conductor,

wherein the insulation film covers a surface of the first plating film and a surface of the second plating film.

5. The inductor according to claim 1 , further comprising:

a first metal post joined to the first conductor and including an end surface exposed through the magnetic body;

a second metal post joined to the second conductor and including an end surface exposed through the magnetic body;

a first electrode formed on a surface of the magnetic body to entirely cover the end surface of the first metal post; and

a second electrode formed on a surface of the magnetic body to entirely cover the end surface of the second metal post.

6. The inductor according to claim 5 , further comprising:

a first conductive bonding material that bonds the first metal post to the first conductor; and

a second conductive bonding material that bonds the second metal post to the second conductor.

7. The inductor according to claim 1 , wherein

the first conductor includes an outer circumferential end having an end surface exposed in a first end surface of the magnetic body,

the second conductor includes an outer circumferential end having an end surface exposed in a second end surface of the magnetic body, and

the inductor further comprises:

a first electrode formed on the first end surface of the magnetic body to cover the end surface of the outer circumferential end of the first conductor; and

a second electrode formed on the second end surface of the magnetic body to cover the end surface of the outer circumferential end of the second conductor.

8. The inductor according to claim 7 , further comprising:

a first metal post joined to the first conductor and including an end surface exposed through the magnetic body; and

a second metal post joined to the second conductor and including an end surface exposed through the magnetic body, wherein

the first electrode continuously covers the first end surface of the magnetic body and a surface of the magnetic body that exposes the end surface of the first metal post and the end surface of the second metal post,

the first electrode is in contact with both of the end surface of the outer circumferential end of the first conductor and the end surface of the first metal post,

the second electrode continuously covers the second end surface of the magnetic body and the surface of the magnetic body that exposes the end surface of the first metal post and the end surface of the second metal post, and

the second electrode is in contact with both of the end surface of the outer circumferential end of the second conductor and the end surface of the second metal post.

9. The inductor according to claim 1 , wherein the first conductor has a rectangular sideward cross section, and the second conductor has a rectangular sideward cross section.