Semiconductor device and manufacturing method thereof

1 . A method comprising:

providing a sensing element comprising a sensing electrode; and

depositing a metal oxide layer over the sensing element to cover the sensing electrode;

forming a metal layer over the metal oxide layer, wherein a barrier height between the metal layer and the metal oxide layer is in a range from about 0.2 eV to about 1.7 eV; and

patterning the metal layer and the metal oxide layer to form a filter over the sensing electrode.

2 . The method of claim 1 , wherein forming the sensing element comprises:

forming an isolation structure over a substrate to define an active region in the substrate;

forming a gate structure over the substrate and across the active region;

forming a reading contact and a sensing contact over the isolation structure; and

forming an interconnection structure over the gate structure, the reading contact, and the sensing contact, wherein the interconnection structure comprises the sensing electrode electrically connected to the sensing contact.

3 . The method of claim 2 , wherein the filter covers the reading contact.

4 . The method of claim 2 , wherein the filter covers the sensing contact.

5 . The method of claim 2 , wherein the reading contact and the sensing contact are on opposite sides of the active region.

6 . The method of claim 2 , wherein the interconnection structure further comprises a word line connected to the reading contact.

7 . The method of claim 1 , wherein forming the metal layer over the metal oxide layer comprises:

depositing the metal layer over an adhesion layer; and

transferring the metal layer with the adhesion layer onto the metal oxide layer.

8 . The method of claim 1 , wherein the metal oxide layer is TiO2, NiO, or combinations thereof.

9 . A method comprising:

providing a structure comprising a gate structure across a semiconductor fin, wherein a bottom of the semiconductor fin is surrounded by isolation structures;

forming a reading contact and a sensing contact over the isolation structures and on opposite sides of the semiconductor fin;

forming a sensing electrode over the structure and electrically connected to the reading contact;

depositing a first work function layer to cover the sensing electrode;

depositing a second work function layer to cover the first work function layer, wherein a work function value of the second work function layer is greater than a work function value of the first work function layer, and an atomic percentage of metal in the second work function layer is greater than an atomic percentage of metal in the first work function layer; and

patterning the second work function layer and the first work function layer to form a filter covering the sensing electrode.

10 . The method of claim 9 , further comprising forming a word line over and electrically connected to the reading contact prior to forming the sensing electrode.

11 . The method of claim 9 , further comprising forming a bit line over and electrically connected to the semiconductor fin prior to forming the sensing electrode.

12 . The method of claim 9 , wherein an area of a top surface of the filter is greater than an area of a top surface of the sensing electrode.

13 . The method of claim 9 , wherein the work function value of the first work function layer is greater than a work function value of the sensing electrode.

14 . The method of claim 9 , further comprising depositing a transition metal dichalcogenide (TMDC) material over the first work function layer prior to depositing the second work function layer.

15 . A method comprising:

patterning a substrate to form a semiconductor structure over the substrate;

forming dielectric structures over the substrate and laterally surrounding a bottom portion of the semiconductor structure;

forming a gate structure over the dielectric structures and the semiconductor structure;

depositing an interlayer dielectric layer over the dielectric structures and laterally surrounding the gate structure;

forming openings in the interlayer dielectric layer to expose the dielectric structures;

forming a reading contact and a sensing contact in the openings;

forming a multilayer interconnection structure over the gate structure, the reading contact, and the sensing contact, wherein the multilayer interconnection structure comprises a sensing electrode electrically connected to the sensing contact;

depositing a first work function layer over the sensing electrode of the multilayer interconnection structure;

depositing a second work function layer over the sensing electrode of the multilayer interconnection structure, wherein a work function value of the second work function layer is greater than a work function value of the first work function layer, and the work function value of the first work function layer is greater than a work function value of the sensing electrode; and

patterning the second work function layer and the first work function layer to form a filter covering the sensing electrode.

16 . The method of claim 15 , wherein the first work function layer is in contact with a top surface of the sensing electrode.

17 . The method of claim 15 , wherein a thickness of the sensing electrode is greater than a thickness of the first work function layer.

18 . The method of claim 15 , further comprising removing an oxide layer over the sensing electrode prior to depositing the first work function layer.

19 . The method of claim 15 , further comprising performing an implantation process to the first work function layer prior to depositing the second work function layer.

20 . The method of claim 15 , wherein the gate structure is a floating gate.