Solid-state imaging device
View Patent ↗Unit pixel cells each includes: a photoelectric conversion film; a transparent electrode; a pixel electrode; an amplification transistor; a reset transistor; and an element isolation STI and a leakage suppression region for electrically isolating the amplification transistor and the reset transistor, the first isolation region being in a silicon substrate, between the amplification transistor and the reset transistor, the reset transistor including: a gate electrode; and a drain region which is connected to the pixel electrode, and is in the silicon substrate, between the gate electrode and element isolation STI and the leakage suppression region, in which a depletion layer formed by a first PN junction between the drain region and its surrounding region and in contact with a surface of the silicon substrate is narrower than a depletion layer formed by a second PN junction between the drain region and its surrounding region and formed in the silicon substrate.
1. A solid-state imaging device comprising:
a semiconductor substrate having a first surface and a second surface opposite to the first surface; and
unit pixel cells two-dimensionally arranged, each unit pixel cell including:
a photoelectric conversion film, above the first surface of the semiconductor substrate, for photo-electrically converting incident light;
a transparent electrode on the photoelectric conversion film;
a pixel electrode between the first surface of the semiconductor substrate and the photoelectric conversion film;
an amplification transistor, comprising a first gate electrode connected to the pixel electrode, for outputting a signal voltage according to a potential of the pixel electrode;
a reset transistor, comprising source or drain region of a first conductivity type in the semiconductor substrate and a second gate electrode, the source or drain region being connected to the pixel electrode for resetting a potential of the first gate electrode; and
a first isolation region, comprising a first region of a second conductivity type in the semiconductor substrate, for electrically isolating the amplification transistor and the reset transistor, wherein
an impurity concentration of the first region is higher than an impurity concentration of a second conductivity type second region of the second conductivity type between the source or drain region and the second surface of the semiconductor substrate,
the source or drain region comprises a first impurity region coupled to the pixel electrode, and a second impurity region disposed between the first impurity region and the first region, and
an impurity concentration of the first impurity region is greater than an impurity concentration of the second impurity region.
2. The solid-state imaging device according to claim 1 , wherein
the reset transistor further includes a channel region of the second conductivity type between the second gate electrode and the second surface of the semiconductor substrate, and
an impurity concentration of the channel region is higher than an impurity concentration of the second region of the semiconductor substrate.
3. The solid-state imaging device according to claim 2 , wherein the reset transistor has a higher threshold voltage than the amplification transistor does.
4. The solid-state imaging device according to claim 3 , further comprising a second isolation region for electrically isolating two adjacent unit pixel cells included in the unit pixel cells, the second isolation region being a trench in the semiconductor substrate, between the two adjacent unit pixel cells.
5. The solid-state imaging device according to claim 2 , further comprising a second isolation region for electrically isolating two adjacent unit pixel cells included in the unit pixel cells, the second isolation region being a trench in the semiconductor substrate, between the two adjacent unit pixel cells.
6. The solid-state imaging device according to claim 1 , wherein when the reset transistor is in OFF state, the second gate electrode has a negative potential relative to a potential of the semiconductor substrate.
7. The solid-state imaging device according to claim 6 , further comprising a second isolation region for electrically isolating two adjacent unit pixel cells included in the plurality of unit pixel cells, the second isolation region being a trench in the semiconductor substrate, between the two adjacent unit pixel cells.
8. The solid-state imaging device according to claim 1 , wherein
a first PN junction is between the first region and an edge of the second impurity region, and
the first region has a lower impurity concentration than the second impurity region does.
9. The solid-state imaging device according to claim 8 , further comprising a second isolation region for electrically isolating two adjacent unit pixel cells included in the unit pixel cells, the second isolation region being a trench in the semiconductor substrate, between the two adjacent unit pixel cells.
10. The solid-state imaging device according to claim 1 , wherein
the source or drain region comprises a third impurity region between the first impurity contact region and the second gate electrode,
a first PN junction is between the semiconductor substrate and an edge of the first impurity region on a side where the first isolation region is located,
the first region is spaced apart from the first impurity region.
11. The solid-state imaging device according to claim 10 , wherein a distance between the first region and the first impurity region is greater than 0.1 μm.
12. The solid-state imaging device according to claim 11 , further comprising a second isolation region for electrically isolating two adjacent unit pixel cells included in the unit pixel cells, the second isolation region being a trench in the semiconductor substrate, between the two adjacent unit pixel cells.
13. The solid-state imaging device according to claim 10 , further comprising a second isolation region for electrically isolating two adjacent unit pixel cells included in the unit pixel cells, the second isolation region being a trench in the semiconductor substrate, between the two adjacent unit pixel cells.
14. The solid-state imaging device according to claim 1 , wherein the first isolation region further comprises a trench in the semiconductor substrate.
15. The solid-state imaging device according to claim 14 , further comprising a second isolation region for electrically isolating two adjacent unit pixel cells included in the unit pixel cells, the second isolation region being a trench in the semiconductor substrate, between the two adjacent unit pixel cells.
16. The solid-state imaging device according to claim 1 , wherein a depletion layer formed by a first PN junction nearby the first region is narrower than a depletion layer formed by a second PN junction nearby the second region.
17. The solid-state imaging device according to claim 1 , wherein the second gate, the source or drain region, and the first region are arranged in that order in cross-sectional view.
18. The solid-state imaging device according to claim 1 , wherein the semiconductor substrate is a semiconductor substrate of the second conductivity type.
19. The solid-state imaging device according to claim 1 , wherein
the semiconductor substrate has a well of the second conductivity type, and
at least the source or drain region, the first region, and the second conductivity type second region are included in the well.
20. The solid-state imaging device according to claim 1 , wherein the second region is disposed immediately adjacent to the source or drain region.
21. A solid-state imaging device comprising:
a semiconductor substrate having a first surface and a second surface opposite to the first surface; and
unit pixel cells two-dimensionally arranged, each unit pixel cell including:
a photoelectric conversion film, above the first surface of the semiconductor substrate, for photo-electrically converting incident light;
a transparent electrode on the photoelectric conversion film;
a pixel electrode between the first surface of the semiconductor substrate and the photoelectric conversion film;
an amplification transistor, comprising a first gate electrode connected to the pixel electrode and a first source or drain region, for outputting a signal voltage according to a potential of the pixel electrode;
a reset transistor, comprising a second source or drain region of a first conductivity type in the semiconductor substrate and a second gate electrode, the second source or drain region being connected to the pixel electrode for resetting a potential of the first gate electrode; and
a first isolation region, comprising a first region of a second conductivity type in the semiconductor substrate, for electrically isolating the amplification transistor and the reset transistor, wherein
an impurity concentration of the first region is higher than an impurity concentration of a second region of the second conductivity type between the first source or drain region and the second surface of the semiconductor substrate,
a lowermost bottom of the first source or drain region of the amplification transistor is located shallower than a lowermost bottom of the second source or drain region of the reset transistor is, in the semiconductor substrate.
22. The solid-state imaging device according to claim 21 , wherein
the reset transistor further includes a channel region of the second conductivity type between the second gate electrode and the second surface of the semiconductor substrate, and
an impurity concentration of the channel region is higher than an impurity concentration of the second region of the semiconductor substrate.
23. The solid-state imaging device according to claim 22 , wherein the reset transistor has a higher threshold voltage than the amplification transistor does.
24. The solid-state imaging device according to claim 23 , further comprising a second isolation region for electrically isolating two adjacent unit pixel cells included in the unit pixel cells, the second isolation region being a trench in the semiconductor substrate, between the two adjacent unit pixel cells.
25. The solid-state imaging device according to claim 22 , further comprising a second isolation region for electrically isolating two adjacent unit pixel cells included in the unit pixel cells, the second isolation region being a trench in the semiconductor substrate, between the two adjacent unit pixel cells.
26. The solid-state imaging device according to claim 21 , wherein the first isolation region further comprises a trench in the semiconductor substrate.
27. The solid-state imaging device according to claim 26 , further comprising a second isolation region for electrically isolating two adjacent unit pixel cells included in the unit pixel cells, the second isolation region being a trench in the semiconductor substrate, between the two adjacent unit pixel cells.
28. The solid-state imaging device according to claim 21 , wherein a depletion layer formed by a first PN junction nearby the first region is narrower than a depletion layer formed by a second PN junction nearby the second region.
29. The solid-state imaging device according to claim 21 , wherein
the second source or drain region comprises a first impurity region coupled to the pixel electrode, and a second impurity region disposed between the first impurity region and the first region, and
an impurity concentration of the first impurity region is greater than an impurity concentration of the second impurity region.
30. The solid-state imaging device according to claim 21 , wherein the second gate, the second source or drain region, and the first region are arranged in that order in cross-sectional view.
31. The solid-state imaging device according to claim 21 , wherein the semiconductor substrate is a semiconductor substrate of the second conductivity type.
32. The solid-state imaging device according to claim 21 , wherein
the semiconductor substrate has a well of the second conductivity type, and
at least the second source or drain region, the first region, and the second region are included in the well.
33. The solid-state imaging device according to claim 21 , wherein the second region is disposed immediately adjacent to the second source or drain region.