Solid-state imaging device with charge holding section between trenched transfer gate sections, manufacturing method of same, and electronic apparatus
View Patent ↗A solid-state imaging device includes a pixel having a photoelectric conversion element which generates a charge in response to incident light, a first transfer gate which transfers the charge from the photoelectric conversion element to a charge holding section, and a second transfer gate which transfers the charge from the charge holding section to a floating diffusion. The first transfer gate includes a trench gate structure having at least two trench gate sections embedded in a depth direction of a semiconductor substrate, and the charge holding section includes a semiconductor region positioned between adjacent trench gate sections.
1. A solid-state imaging device, comprising:
a pixel including a photoelectric conversion element configured to generate a charge in response to incident light, a first transfer gate configured to transfer the charge from the photoelectric conversion element to a charge holding section, and a second transfer gate configured to transfer the charge from the charge holding section to a floating diffusion, wherein
the first transfer gate includes a trench gate structure having at least two trench gate sections embedded in a depth direction of a semiconductor substrate, and
the charge holding section includes a semiconductor region positioned between adjacent ones of the plurality of trench gate sections.
2. The solid-state imaging device according to claim 1 , wherein respective ones of the at least two trench gate sections have a dimension in the depth direction which is larger than a dimension in a direction perpendicular to the depth direction.
3. The solid-state imaging device according to claim 1 , wherein a depth of respective ones of the at least two trench gate sections is substantially the same as a depth of the semiconductor region.
4. The solid-state imaging device according to claim 1 , wherein the semiconductor substrate has a first conductivity type and the semiconductor region has a second conductivity type which is opposite the first conductivity type.
5. The solid-state imaging device according to claim 4 , wherein respective portions of the semiconductor substrate are disposed between the semiconductor region and corresponding ones of the at least two trench gate sections.
6. The solid-state imaging device according to claim 5 , wherein the first conductivity type is P-type, and the second conductivity type is N-type.
7. The solid-state imaging device according to claim 5 , wherein the first conductivity type is N-type, and the second conductivity type is P-type.
8. The solid-state imaging device according to claim 1 , wherein the semiconductor region also serves as one of a source or a drain of the second transfer gate.
9. The solid-state imaging device according to claim 1 , wherein the first transfer gate further includes a light-shielding section.
10. The solid-state imaging device according to claim 9 , wherein the light-shielding section includes portion respective portions embedded in corresponding ones of the at least two trench gate sections.
11. The solid-state imaging device according to claim 9 , wherein the light-shielding section includes a portion covering an upper surface and side surfaces of the first transfer gate.
12. The solid-state imaging device according to claim 9 , wherein a material of the light-shielding section is tungsten.
13. The solid-state imaging device according to claim 1 , wherein the at least two trench gate sections is at least three trench gate sections.
14. The solid-state imaging device according to claim 1 , wherein a material of the first transfer gate is polysilicon.
15. The solid-state imaging device according to claim 1 , wherein the pixel further comprises a discharge gate configured to discharge charges accumulated in the photoelectric conversion element.
16. The solid-state imaging device according to claim 1 , wherein the pixel further comprises a reset gate configured to discharge charges held in the floating diffusion.
17. The solid-state imaging device according to claim 1 , wherein the pixel is a back-side illumination type.
18. A method of manufacturing a solid-state imaging device, comprising:
providing a semiconductor substrate;
forming a pixel on the semiconductor substrate, the pixel including a photoelectric conversion element configured to generate a charge in response to incident light, a first transfer gate configured to transfer the charge from the photoelectric conversion element to a charge holding section, and a second transfer gate configured to transfer the charge from the charge holding section to a floating diffusion, wherein
the first transfer gate includes a trench gate structure having at least two trench gate sections embedded in a depth direction of a semiconductor substrate, and
the charge holding section includes a semiconductor region positioned between adjacent ones of the plurality of trench gate sections.
19. An electronic apparatus, comprising:
an optical section;
a solid-state imaging device; and
a digital signal processor circuit,
wherein the solid-state imaging device includes:
a pixel including a photoelectric conversion element configured to generate a charge in response to incident light, a first transfer gate configured to transfer the charge from the photoelectric conversion element to a charge holding section, and a second transfer gate configured to transfer the charge from the charge holding section to a floating diffusion, wherein
the first transfer gate includes a trench gate structure having at least two trench gate sections embedded in a depth direction of a semiconductor substrate, and
the charge holding section includes a semiconductor region positioned between adjacent ones of the plurality of trench gate sections.