IMAGING DEVICE

Abstract

An imaging device capable of multiplying carriers and miniaturizing the device is obtained. The imaging device includes a carrier storage portion for storing carriers generated by photoelectric conversion, having a photoelectric conversion function, a multiplier section including a multiplier electrode applying an electric field for multiplying carriers due to impact ionization by an electric field, one first transfer electrode so provided between the carrier storage portion and the multiplier electrode as to be adjacent to the carrier storage portion and the multiplier electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an overall structure of a CMOS image sensor according to a first embodiment of the present invention;

FIG. 2 is a sectional view showing the structure of the CMOS image sensor according to the first embodiment shown in FIG. 1;

FIG. 3 is a plan view showing pixels of the CMOS image sensor according to the first embodiment shown in FIG. 1;

FIG. 4 is a circuit diagram showing the structure of the CMOS image sensor according to the first embodiment shown in FIG. 1;

FIG. 5 is a sectional view for illustrating a multiplication operation of the CMOS image sensor according to the first embodiment shown in FIG. 1;

FIG. 6 is a signal waveform diagram for illustrating the multiplication operation of the CMOS image sensor according to the first embodiment shown in FIG. 1;

FIG. 7 is a sectional view for illustrating a reverse transfer operation of the CMOS image sensor according to the first embodiment shown in FIG. 1;

FIG. 8 is a signal waveform diagram for illustrating the reverse transfer operation of the CMOS image sensor according to the first embodiment shown in FIG. 1;

FIG. 9 is a sectional view showing a structure of a CMOS image sensor according to a second embodiment of the present invention;

FIG. 10 is a circuit diagram for illustrating an imaging operation of the CMOS image sensor according to the second embodiment of the present invention;

FIG. 11 is a sectional view showing a structure of a CMOS image sensor according to a third embodiment of the present invention;

FIG. 12 is a sectional view showing a conventional CCD image sensor; and

FIG. 13 is a sectional view in a case where a structure of the exemplary conventional CCD image sensor shown in FIG. 12 is applied to a CMOS image sensor.

Claims

1. An imaging device comprising: a carrier storage portion for storing carriers generated by photoelectric conversion, having a photoelectric conversion function;a multiplier section including a multiplier electrode applying an electric field for multiplying carriers due to impact ionization by an electric field; andone first transfer electrode so provided between said carrier storage portion and said multiplier electrode as to be adjacent to said carrier storage portion and said multiplier electrode.

2. The imaging device according to claim 1, wherein a voltage of said first transfer electrode is so controlled as to transfer carriers from said carrier storage portion to said multiplier section after a voltage enabling multiplication of carriers due to impact ionization is applied to said multiplier electrode.

3. The imaging device according to claim 2, wherein voltages of said first transfer electrode and said multiplier electrode are so controlled as to return said carrier multiplied due to impact ionization to said carrier storage portion, anda voltage of said first transfer electrode is so controlled as to transfer said carrier returned from said multiplier section to said carrier storage portion to said multiplier section again.

4. The imaging device according to claim 3, wherein a voltage of said first transfer electrode is so controlled as to transfer said carriers from said multiplier section to said carrier storage portion after a voltage smaller than a voltage applied to adjacent said first transfer electrode is applied to said multiplier electrode.

5. The imaging device according to claim 1, further comprising: a carrier-number-based voltage converting portion converting the number of multiplied carriers to a voltage; anda readout electrode for transferring carriers to said carrier-number-based voltage converting portion, whereinsaid carrier storage portion, said multiplier section having said multiplier electrode, said first transfer electrode, said carrier-number-based voltage converting portion, and said readout electrode are included in one pixel.

6. The imaging device according to claim 5, further comprising a common first wiring layer connected to said multiplier electrodes of a plurality of said pixels, for applying a voltage enabling impact ionization of carriers to a plurality of said multiplier electrodes.

7. The imaging device according to claim 5, further comprising a common second wiring layer connected to said first transfer electrodes of a plurality of said pixels, for applying a voltage to a plurality of said first transfer electrodes.

8. The imaging device according to claim 5, further comprising a common third wiring layer connected to said readout electrodes of a plurality of said pixels, for applying a voltage to a plurality of said readout electrodes.

9. The imaging device according to claim 5, wherein said readout electrode is so provided between said multiplier electrode and said carrier-number-based voltage converting portion as to be adjacent to said multiplier electrode and said carrier-number-based voltage converting portion.

10. The imaging device according to claim 9, wherein a first transfer channel is so provided below said first transfer electrode, said multiplier electrode and said readout electrode as to couple said carrier storage portion and said carrier-number-based voltage converting portion.

11. The imaging device according to claim 10, wherein said carrier storage portion is adjusted to a first potential, andsaid first transfer electrode adjusts said first transfer channel located under said first transfer electrode to a second potential higher than said first potential of said carrier storage portion in a case of an ON-state, and adjusts said first transfer channel located under said first transfer electrode to a third potential lower than said first potential of said carrier storage portion in a case of an OFF-state.

12. The imaging device according to claim 11, wherein said multiplier electrode adjusts said first transfer channel located under said multiplier electrode to a fourth potential higher than said second potential and multiplying carriers due to impact ionization in a case of an ON-state, and adjusts said first transfer channel located under said multiplier electrode to said third potential lower than said second potential in a case of an OFF-state.

13. The imaging device according to claim 12, wherein said carrier-number-based voltage converting portion is adjusted to a fifth potential, andsaid readout electrode adjusts said first transfer channel located under said readout electrode to said second potential lower than said fifth potential and higher than said third potential in a case of an ON-state, and adjusts said first transfer channel located under said readout electrode to said third potential in a case of an OFF-state.

14. The imaging device according to claim 5, wherein said readout electrode is so provided between said carrier storage portion and said carrier-number-based voltage converting portion as to be adjacent to said carrier storage portion and said carrier-number-based voltage converting portion.

15. The imaging device according to claim 14, wherein a second transfer channel is so provided below said first transfer electrode and said multiplier electrode as to be adjacent to said carrier storage portion.

16. The imaging device according to claim 14, wherein a third transfer channel is so provided below said readout electrode as to couple said carrier storage portion and said carrier-number-based voltage converting portion.

17. The imaging device according to claim 16, wherein said carrier storage portion is adjusted to a sixth potential,said carrier-number-based voltage converting portion is adjusted to a seventh potential, andsaid readout electrode adjusts said third transfer channel located under said readout electrode to an eighth potential lower than said seventh potential and higher than said sixth potential in a case of an ON-state, and adjusts said third transfer channel under said readout electrode to a ninth potential lower than said sixth potential in a case of an OFF-state.

18. The imaging device according to claim 1, further comprising a second transfer electrode so provided above said carrier storage portion as to be adjacent to said first transfer electrode

19. The imaging device according to claim 5, further comprising an element separation region for separating pixels.