Multi-protrusion transfer gate structure

1. An integrated circuit (IC) structure comprising:

a substrate region having a first doping type and comprising an upper surface;

first and second regions within the substrate region, each of the first and second regions having a second doping type opposite the first doping type; and

a gate conductor comprising a plurality of conductive protrusions extending into the substrate region in a direction perpendicular to a plane of the upper surface,

wherein

the conductive protrusions of the plurality of conductive protrusions are electrically connected to each other,

at least a portion of each conductive protrusion of the plurality of conductive protrusions is positioned between the first and second regions, and

a first conductive protrusion of the plurality of conductive protrusions is positioned between the first region and a second conductive protrusion of the plurality of conductive protrusions.

2. The IC structure of claim 1 , wherein the plurality of conductive protrusions is electrically isolated from the substrate region by a dielectric layer.

3. The IC structure of claim 2 , wherein the gate conductor further comprises a conductive region continuous with each conductive protrusion of the plurality of conductive protrusions and electrically isolated from the substrate region by the dielectric layer.

4. The IC structure of claim 1 , wherein

the first region comprises a source feature between a photodiode and the gate conductor, and

the second region comprises a drain feature adjacent to the gate conductor.

5. The IC structure of claim 4 , wherein the drain feature comprises an n-type lightly doped drain.

6. The IC structure of claim 1 , wherein

the first region comprises a cathode of a photodiode of a pixel device, and

the second region comprises a floating diffusion node of the pixel device.

7. The IC structure of claim 1 , wherein

the first region comprises a cathode of a photodiode of a pixel device, and

at least one conductive protrusion of the plurality of conductive protrusions extends into the cathode of the photodiode.

8. The IC structure of claim 1 , wherein

each conductive protrusion of the plurality of conductive protrusions comprises a protrusion diameter, and

each conductive protrusion of the plurality of conductive protrusions is separated from the remainder of the plurality of conductive protrusions by one or more distances equal to or greater than one half of the protrusion diameter.

9. The IC structure of claim 1 , wherein each conductive protrusion of the plurality of conductive protrusions has approximately a same length.

10. A pixel sensor circuit comprising:

first and second power supply nodes;

a reset transistor coupled between the first power supply node and an internal node;

a photodiode coupled to the second power supply node; and

a transfer transistor coupled between the photodiode and the internal node, wherein the transfer transistor comprises multiple vertical gate structures configured to selectively couple the photodiode to the internal node.

11. The pixel sensor circuit of claim 10 , further comprising first and second transistors coupled in series between the first power supply node and an output node, the first transistor comprising a gate coupled to the internal node.

12. The pixel sensor circuit of claim 10 , wherein

the internal node comprises a floating diffusion node, and

the multiple vertical gate structures are positioned between the photodiode and the floating diffusion node.

13. The pixel sensor circuit of claim 12 , wherein

the photodiode is one photodiode of a plurality of photodiodes coupled to the second power supply node,

the transfer transistor is one transfer transistor of a plurality of transfer transistors, and

each transfer transistor of the plurality of transfer transistors comprises multiple vertical gate structures configured to selectively couple a corresponding photodiode of the plurality of photodiodes to the floating diffusion node.

14. The pixel sensor circuit of claim 10 , wherein at least one of the multiple vertical gate structures extends into the photodiode.

15. The pixel sensor circuit of claim 10 , wherein

the transfer transistor is one transfer transistor of a plurality of transfer transistors,

the pixel sensor circuit is one pixel sensor of an array of pixel sensor circuits, and

each pixel sensor circuit of the array of pixel sensor circuits comprises a corresponding transfer transistor of the plurality of transfer transistors comprising multiple vertical gate structures configured to selectively couple a corresponding photodiode to a corresponding internal node.

16. The pixel sensor circuit of claim 10 , wherein the pixel sensor circuit has a back-side illumination configuration.

17. An integrated circuit (IC) structure comprising:

a p-type substrate region comprising an upper surface;

n-type source and drain features positioned within the substrate region and separated from each other along a first direction;

a gate conductor comprising:

a plurality of conductive protrusions extending into the substrate region perpendicular to the upper surface; and

a conductive region extending above the upper surface and continuous with each conductive protrusion of the plurality of conductive protrusions; and

a dielectric layer between the substrate region and each of the plurality of conductive protrusions and the conductive region,

wherein

at least a portion of each conductive protrusion of the plurality of conductive protrusions is positioned between the source and drain features, and

first and second conductive protrusions of the plurality of conductive protrusions are aligned with each other along the first direction.

18. The IC structure of claim 17 , wherein the plurality of conductive protrusions comprises a total number of conductive protrusions ranging from three to twelve.

19. The IC structure of claim 17 , wherein the conductive protrusions of the plurality of conductive protrusions are arranged in rows and columns.

20. The IC structure of claim 17 , wherein an entirety of the conductive region is positioned above the upper surface.