Common-mode filter

1. A common-mode filter comprising:

a first conductor layer having a first spiral part formed so as to draw a convolution and a first lead electrode extending from one end of the first spiral part;

a second conductor layer having a second spiral part formed so as to draw a convolution and a second lead electrode extending from one end of the second spiral part; and

an insulating layer placed between the first and second conductor layers;

wherein the first conductor layer is formed with third and fourth lead electrodes;

wherein the second conductor layer is formed with a connecting conductor connecting the third lead electrode to the other end of the first spiral part;

wherein the fourth lead electrode is connected to the other end of the second spiral part through a contact hole formed in the insulating layer;

wherein the third lead electrode is connected to one end of the connecting conductor through a contact hole formed in the insulating layer; and

wherein the other end of the connecting conductor is connected to the other end of the first spiral part through a contact hole formed in the insulating layer.

2. A common-mode filter according to claim 1 , wherein the first and second conductor layers have respective regions overlapping each other.

3. A common-mode filter according to claim 2 , wherein the first spiral part has a first bent portion bent toward a center of the first spiral part;

wherein the second spiral part has a second bent portion bent toward a side opposite from a center of the second spiral part at a position corresponding to the first bent portion; and

wherein a region other than the first bent portion in the first spiral part and a region other than the second bent portion in the second spiral part overlap each other.

4. A common-mode filter according to claim 3 , wherein a conductor forming the first spiral part and a conductor forming the second spiral part have substantially the same length.

5. A common-mode filter according to claim 1 , wherein the first and second conductor layers are formed with a plurality of first spiral parts, first lead electrodes, second spiral parts, second lead electrodes, third lead electrodes, fourth lead electrodes, and connecting conductors corresponding thereto.

6. A common-mode filter according to claim 1 , further comprising:

a third conductor layer having a third spiral part formed so as to draw a convolution and a fifth lead electrode extending from one end of the third spiral part;

a fourth conductor layer having a fourth spiral part formed so as to draw a convolution and a sixth lead electrode extending from one end of the fourth spiral part;

an insulating layer placed between the second and third conductor layers; and

an insulating layer placed between the third and fourth conductor layers;

wherein the fourth conductor layer is formed with seventh and eighth lead electrodes;

wherein the fourth conductor layer is formed with a second connecting conductor connecting the seventh lead electrode to the other end of the third spiral part;

wherein the eighth lead electrode is connected to the other end of the fourth spiral part through a contact hole formed in the insulating layer placed between the third and fourth conductor layers;

wherein the seventh lead electrode is connected to one end of the second connecting conductor through a contact hole formed in the insulating layer placed between the third and fourth conductor layers; and

wherein the other end of the second connecting conductor is connected to the other end of the third spiral part through a contact hole formed in the insulating layer placed between the third and fourth conductor layers.