Fingerprint sensor and fabrication method thereof

1. A fingerprint sensor using ultrasonic waves, comprising:

a complementary metal-oxide semiconductor structure which is formed on a substrate that is doped with a first type dopant;

an insulating layer which is formed on the complementary metal-oxide semiconductor structure;

a lower electrode which is formed in a central portion of the insulating layer;

a piezoelectric region which is formed on the lower electrode;

an upper electrode which is formed on the piezoelectric layer; and

a fingerprint contact layer which is formed to cover a portion of an upper surface of the insulating layer on which the lower electrode has not been formed, the lower electrode, the piezoelectric region, and the upper electrode.

2. The fingerprint sensor of claim 1 , wherein the complementary metal-oxide semiconductor structure comprises:

a region which is formed in a portion of the surface of the substrate by doping with a second type dopant;

a source and a drain which are formed in the surface of the region doped with the second type dopant by doping with the first type dopant; and

a source and a drain which are formed in a portion of the surface of the substrate by doping the portion the second type dopant so as to be opposite to the source and the drain doped with the first type dopant.

3. The fingerprint sensor of claim 2 , wherein the lower electrode is electrically connected to the drain doped with the first type dopant and the source doped with the second type dopant.

4. The fingerprint sensor of claim 3 , wherein the lower electrode is electrically connected to the drain doped with the first type dopant and the source doped with the second type dopant through via holes which penetrate through the insulating layer and are filled with a conductive material.

5. The fingerprint sensor of claim 1 , wherein the piezoelectric region comprises at least one of PZT, PST, Quartz, (Pb, Sm)TiO 3 , PMN(Pb(MgNb)O 3 )-PT(PbTiO 3 ), PVDF, and PVDF-TrFe.

6. The fingerprint sensor of claim 1 , wherein the fingerprint contact layer comprises a material having a similar acoustic impedance to that of the skin tissue of a person's finger.

7. The fingerprint sensor of claim 6 , wherein the fingerprint contact layer comprises at least one of polymer materials comprising polyurethane, polystyrene, and rubber.

8. The fingerprint sensor of claim 1 , wherein the fingerprint sensor has a matrix structure in which unit elements are arrayed.

9. A method of fabricating a fingerprint sensor using ultrasonic waves, comprising:

forming a complementary metal-oxide semiconductor structure on a substrate that is doped with a first type dopant;

forming an insulating layer on the complementary metal-oxide semiconductor structure and sequentially forming a lower electrode, a piezoelectric region, and an upper electrode on the insulating layer;

removing side portions of the lower electrode, the piezoelectric region, and the upper electrode; and

forming a fingerprint contact layer to cover a portion of an upper surface of the insulating layer, the lower electrode, the piezoelectric region, and the upper electrode.

10. The method of claim 9 , wherein the formation of the insulating layer comprises:

forming the insulating layer on the complementary metal-oxide semiconductor structure;

forming first and second via holes in the insulating layer to respectively face a drain of the complementary metal-oxide semiconductor structure having the first polarity and a source of the complementary metal-oxide semiconductor structure having a second polarity and then filling the first and second via holes with a conductive material; and

sequentially forming the lower electrode, the piezoelectric region, and the upper electrode on the insulating layer and the first and second via holes.

11. The method of claim 9 , wherein the piezoelectric region comprises at least one of PZT, PST, Quartz, (Pb, Sm)TiO 3 , PMN(Pb(MgNb)O 3 )-PT(PbTiO 3 ), PVDF, and PVDF-TrFe.

12. The method of claim 9 , wherein the fingerprint contact layer comprises at least one of polymer materials comprising polyurethane, polystyrene, and rubber that have a similar acoustic impedance to that of the skin tissue of a person's finger.