Solid-state imaging device and imaging apparatus

1. A solid-state imaging device in which pixels each comprising a photoelectric conversion portion formed above a semiconductor substrate and an MOS type signal reading circuit formed at the semiconductor substrate and provided for reading out a signal corresponding to electric charges generated in the photoelectric conversion portion are disposed in an array form, wherein:

the photoelectric conversion portion comprises a pixel electrode formed above the semiconductor substrate so as to be split in accordance with each of the pixels, a counter electrode formed above the pixel electrode, and a photoelectric conversion layer formed between the pixel electrode and the counter electrode;

a bias voltage higher than a power supply voltage of the signal reading circuit is applied to the counter electrode so that holes of the electric charges generated in the photoelectric conversion layer move to the pixel electrode;

the signal reading circuit comprises a charge storage portion which is formed in the semiconductor substrate and in which the holes moved to the pixel electrode are stored, an output transistor which outputs a signal corresponding to the potential of the charge storage portion, and a reset transistor which is provided for resetting the potential of the charge storage portion to a predetermined reset potential;

the charge storage portion comprises a first charge storage region made from an n-type impurity region electrically connected to the pixel electrode, a second charge storage region made from an n-type impurity region formed next to but spaced from the first charge storage region, and a separation/connection region which electrically separates the first charge storage region and the second charge storage region from each other when the potential is higher than a predetermined potential in a sectional potential but which electrically connects the first charge storage region and the second charge storage region to each other when the potential is not higher than the predetermined potential in the sectional potential; holes moved from the pixel electrode are stored in each of the first charge storage region, the second charge storage region and the separation/connection region till the quantity of holes moved to the pixel electrode reaches a predetermined quantity, but holes moved from the pixel electrode are stored only in the first charge storage region when the quantity of holes moved to the pixel electrode exceeds the predetermined quantity; and

the output transistor outputs a signal corresponding to the potential of the second charge storage region.

2. The solid-state imaging device according to claim 1 , wherein the predetermined potential is higher than the reset potential.

3. The solid-state imaging device according to claim 1 , wherein the separation/connection region is made by a gate electrode which is formed over the semiconductor substrate between the first charge storage region and the second charge storage region and to which a fixed voltage is applied.

4. The solid-state imaging device according to claim 3 , wherein the fixed voltage is the power supply voltage.

5. The solid-state imaging device according to claim 1 , wherein the separation/connection region is made by an impurity region formed between the first charge storage region and the second charge storage region in the semiconductor substrate.

6. The solid-state imaging device according to claim 5 , wherein:

the impurity region is of the same conductivity type as that of each of the first charge storage region and the second charge storage region; and

impurity concentration of the impurity region is lower than that of each of the first charge storage region and the second charge storage region.

7. The solid-state imaging device according to claim 6 , wherein another impurity region of a conductivity type reverse to that of the impurity region is provided on a surface of the impurity region.

8. A solid-state imaging device in which pixels each comprising a photoelectric conversion portion formed above a semiconductor substrate and an MOS type signal reading circuit formed at the semiconductor substrate and provided for reading out a signal corresponding to electric charges generated in the photoelectric conversion portion are disposed in an array form, wherein:

the photoelectric conversion portion comprises a pixel electrode formed above the semiconductor substrate so as to be split in accordance with each of the pixels, a counter electrode formed above the pixel electrode, and a photoelectric conversion layer formed between the pixel electrode and the counter electrode;

a bias voltage lower than a reference voltage of the signal reading circuit is applied to the counter electrode so that electrons of the electric charges generated in the photoelectric conversion layer move to the pixel electrode;

the signal reading circuit comprises a charge storage portion which is formed in the semiconductor substrate and in which the electrons moved to the pixel electrode are stored, an output transistor which outputs a signal corresponding to the potential of the charge storage portion, and a reset transistor which is provided for resetting the potential of the charge storage portion to a predetermined reset potential;

the charge storage portion comprises a first charge storage region made from a p-type impurity region electrically connected to the pixel electrode, a second charge storage region made from a p-type impurity region formed next to but spaced from the first charge storage region, and a separation/connection region which electrically separates the first charge storage region and the second charge storage region from each other when the potential is lower than a predetermined potential in a sectional potential but which electrically connects the first charge storage region and the second charge storage region to each other when the potential is not lower than the predetermined potential in the sectional potential, electrons moved from the pixel electrode are stored in each of the first charge storage region, the second charge storage region and the separation/connection region till the quantity of electrons moved to the pixel electrode reaches a predetermined quantity, but electrons moved from the pixel electrode are stored only in the first charge storage region when the quantity of electrons moved to the pixel electrode exceeds the predetermined quantity; and

the output transistor outputs a signal corresponding to the potential of the second charge storage region.

9. The solid-state imaging device according to claim 8 , wherein the predetermined potential is lower than the reset potential.

10. The solid-state imaging device according to claim 8 , wherein the separation/connection region is made by a gate electrode which is formed over the semiconductor substrate between the first charge storage region and the second charge storage region and to which a fixed voltage is applied.

11. The solid-state imaging device according to claim 10 , wherein the fixed voltage is the reference voltage.

12. The solid-state imaging device according to claim 8 , wherein the separation/connection region is made by an impurity region formed between the first charge storage region and the second charge storage region in the semiconductor substrate.

13. The solid-state imaging device according to claim 12 , wherein:

the impurity region is of the same conductivity type as that of each of the first charge storage region and the second charge storage region; and

impurity concentration of the impurity region is lower than that of each of the first charge storage region and the second charge storage region.

14. The solid-state imaging device according to claim 13 , wherein another impurity region of a conductivity type reverse to that of the impurity region is provided on a surface of the impurity region.

15. An imaging apparatus comprising the solid-state imaging device according to claim 1 .

16. An imaging apparatus comprising the solid-state imaging device according to claim 8 .