JP5361938B2 - Solid-state imaging device and camera - Google Patents

Description

  The present invention relates to a solid-state imaging device and a camera, and is particularly suitable for use in a CMOS area sensor.

  In recent years, a CMOS area sensor in which a photodiode and a MOS transistor are integrated on a single chip is used as a solid-state imaging device. Compared with a CCD, a CMOS area sensor has advantages such as lower power consumption, lower drive power, and higher speed. Therefore, it is expected that the demand for the COMS area sensor will increase in the future.

  For example, a photodiode, a floating diffusion (floating diffusion) region, a transfer transistor for transferring charges from the photodiode to the floating diffusion region, and for resetting the floating diffusion region to a predetermined potential There is a solid-state imaging device having a CMOS area sensor configured by forming a plurality of pixels each having a reset transistor in a matrix.

  And the proposal of expanding the dynamic range of a solid-state image sensor using such a CMOS area sensor is made. As a technique for expanding the dynamic range of a solid-state imaging device, there are techniques described in Patent Documents 1 and 2.

JP 2001-186414 A JP 2004-335802 A

  However, the conventional technique has a problem in that a lot of noise signals are generated in the solid-state imaging device, and the image quality may be deteriorated.

  The present invention has been made in view of such problems, and a solid-state imaging device that realizes expanding the dynamic range and reducing the generation of noise, and a camera using the solid-state imaging device. The purpose is to provide.

The solid-state imaging device of the present invention includes a photoelectric conversion unit that generates charges by incident light, a charge storage region for storing charges generated by the photoelectric conversion unit, the photoelectric conversion unit, and the charge storage region. The first transfer MOS transistor disposed between the first transfer MOS transistor for transferring the charge generated by the photoelectric conversion unit to the charge storage region and the channel of the first transfer MOS transistor are different paths. A path when a part of the charge overflowing from the photoelectric conversion unit moves to the charge storage region, an additional capacitor for storing a part of the charge overflowing from the photoelectric conversion unit, and the charge storage region, disposed between said additional capacitor, and a second transfer MOS transistor for transferring the charges accumulated in the additional capacitance in the charge storage region, and a potential barrier layer to said charge, but first The potential barrier layer is provided in the well except for a portion under the gate electrode of the first transfer MOS transistor, and has a first conductivity type impurity concentration higher than that of the well. The impurity concentration of the first conductivity type in the path is lower than the impurity concentration of the first conductivity type in the potential barrier layer, and the path is the first transfer MOS transistor. In the cross section in the width direction of the gate electrode of the first transfer MOS transistor, it is sandwiched between the potential barrier layers in the width direction in the cross section in the width direction of the first transfer MOS transistor. characterized that you have located between the potential barrier layer.

  The camera of the present invention includes the solid-state imaging device, a lens for forming an optical image on the solid-state imaging device, and a diaphragm for changing the amount of light passing through the lens.

According to the present invention, the electric charge overflowing from the photoelectric conversion part passes through a separately provided path without passing through the channel part of the first transfer MOS transistor. As a result, the first transfer MOS transistor can be closed (off) as reliably as possible, and generation of noise from the first transfer MOS transistor can be suppressed as much as possible. Therefore, it is possible to simultaneously increase the dynamic range by using the electric charge overflowing from the photoelectric conversion unit and reduce the generation of the noise.

1 is a diagram illustrating an example of a schematic configuration of a pixel provided in a solid-state imaging device according to an embodiment of the present invention. 5 is a timing chart illustrating an example of a pixel readout operation of the solid-state imaging device according to the embodiment of this invention. 1 is a plan view illustrating an example of a schematic configuration of a pixel according to an embodiment of the present invention. FIG. 4 is a diagram illustrating an embodiment of the present invention, in which pixels seen from the direction AB in FIG. 3 are simplified. FIG. 10 is a plan view illustrating another example of a schematic configuration of a pixel according to an embodiment of the present invention. It is a block diagram which shows other embodiment of this invention and shows an example of a structure of a still video camera. It is a block diagram which shows other embodiment of this invention and shows an example of a structure of a video camera.

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating an example of a schematic configuration of pixels provided in the solid-state imaging device of the present embodiment. For comparison with the present embodiment, there is a method of controlling (raising) the gate potential of the transfer transistor to, for example, about 0 [V] when charges are accumulated in the photodiode. Then, the transfer transistor is not completely turned off, and a part of the electric charge overflowing from the photodiode flows into the floating diffusion region. The charge overflowing from the photodiode is used as a pixel signal together with the charge accumulated in the photodiode, so that the dynamic range of the CMOS area sensor can be expanded.
However, in such a method, since the overflowing charge passes through the channel portion of the MOS transistor, the influence of dark current is increased. On the other hand, according to the configuration of the present embodiment, the influence of dark current can be reduced.

  In FIG. 1, the solid-state imaging device of this embodiment includes a photodiode PD, a first transfer MOS transistor M1, a reset MOS transistor M2, a second transfer MOS transistor M3, and a source follower MOS transistor M4. A plurality of pixels including the MOS transistor M5 are arranged in a two-dimensional matrix of n rows × m columns (n and m are natural numbers).

The photodiode PD is connected to the floating diffusion region FD for temporarily storing charges through the first transfer MOS transistor M1. A reset MOS transistor M2, a source follower MOS transistor M4, and a second transfer MOS transistor M3 are also connected to the floating diffusion region FD. The second transfer MOS transistor M3 is connected to an additional capacitor CS that accumulates charges overflowing from the photodiode PD.
The source follower MOS transistor M4 is mutually connected to the selection MOS transistor M5, and amplifies a signal based on the charge transferred to the floating diffusion region FD. Further, an additional capacitor is separately provided between the floating diffusion region FD and the first transfer MOS transistor M1 (or the second transfer MOS transistor M3), and separately provided between the additional capacitor and the floating diffusion region FD. A configuration in which a switch (MOS transistor) is provided is also possible. Further, the amplification element may not be provided in the pixel, and the destination transferred by the first transfer MOS transistor M1 may be a storage capacitor provided in the signal line.

  The first transfer MOS transistor M1, the reset MOS transistor M2, the second transfer MOS transistor M3, and the selection MOS transistor M5 are each turned on and off by a control signal (gate signal) supplied to the gate. Note that the first transfer MOS transistor M1, the reset MOS transistor M2, the second transfer MOS transistor M3, and the selection MOS transistor M5 are turned on (conducted) when a high-level gate signal is supplied to the gate, and low level. When the gate signal is supplied to the gate, it is assumed to be turned off (shut off). In this conductive state, a channel serving as a charge path is formed in the vicinity of the gate insulating film.

  Specifically, the control signal φTX is supplied to the gate of the first transfer MOS transistor M1, the control signal φS is supplied to the second transfer MOS transistor M3, and the control signal φS is supplied to the gate of the selection MOS transistor M5. A signal φX is supplied, and a control signal φRES is supplied to the gate of the reset MOS transistor M2.

Here, the control signal φTX is a control signal for transferring the charge accumulated in the photodiode PD to the floating diffusion region FD. The control signal φS is a control signal for transferring the charge overflowing from the photodiode PD and accumulated in the additional capacitor CS to the floating diffusion region FD. The control signal φX is a control signal for selecting a pixel. The control signal φRES is a control signal for resetting the potential of the floating diffusion region FD to the power supply potential V _CC (for example, +5 V).

  In the solid-state imaging device of the present embodiment, a level obtained by adding the signal level (S) transferred to the floating diffusion region FD and the reset level (N) outside the pixel region where the pixels as shown in FIG. 1 are formed. There is provided a memory circuit having a signal level holding capacitor for holding the above-mentioned signal and a reset level holding capacitor for holding the reset level (N) signal.

  Then, a signal obtained by adding the signal level (S) held in the signal level holding capacitor Cs and the reset level (N), and a signal of the reset level (N) held in the reset level holding capacitor A differential amplifier for amplifying the differential signal (signal level (S) signal) is provided. The solid-state imaging device outputs a signal obtained by this differential amplifier.

Here, an example of the pixel readout operation of the solid-state imaging device of the present embodiment will be described with reference to the timing chart of FIG.
First, at time t1, the high level control signal φS is supplied to the second transfer MOS transistor M3 and the high level control signal φX is supplied to the selection MOS transistor M5. A signal φRES is supplied to the gate of the reset MOS transistor M2. Then, the reset MOS transistor M2, the second transfer MOS transistor M3, and the selection MOS transistor M5 are turned on. That is, when the selection MOS transistor M5 is turned on, the floating diffusion region FD and the additional capacitor CS are reset to the power supply voltage V _CC while the pixel to which the selection MOS transistor M5 belongs is selected.

At time t2, the low level control signal φRES is supplied to the reset MOS transistor M2, the reset MOS transistor M2 is turned off, and the reset operation of the floating diffusion region FD and the additional capacitor CS is completed. When this reset operation is performed, the reset level (N2) in the floating diffusion region FD and the additional capacitor CS is read.
At time t3, the low-level control signal φX is supplied to the selection MOS transistor M5. As a result, the selection MOS transistor M5 is turned off, and accumulation of charges generated in the photodiode PD is started. At time t3 to t4, charges are accumulated in the photodiode PD, and charges overflowing from the photodiode PD flow into the path 31 shown in FIG. 4 and the region where the additional capacitor CS is formed. The electric charge flowing into the path 31 is accumulated in the floating diffusion FD. On the other hand, the charge flowing into the region where the additional capacitor CS is formed is accumulated in the region (additional capacitor CS).

At time t4, a high-level control signal φX is supplied to the selection MOS transistor M5, and a low-level control signal φS is supplied to the second transfer MOS transistor M3. As a result, the selection MOS transistor M5 is turned on and the second transfer MOS transistor M3 is turned off, and the operation of accumulating the charge generated in the photodiode PD is completed.
At time t5, the control signal φRES is supplied to the reset MOS transistor M2. As a result, the reset MOS transistor M2 is turned on, and the floating diffusion region FD is reset to the power supply voltage V _CC .

At time t6, the low level control signal φRES is supplied to the reset MOS transistor M2, the reset MOS transistor M2 is turned off, and the reset operation of the floating diffusion region FD is completed. By this reset operation, the reset level (N1) in the floating diffusion region FD is read.
At time t7, a high-level control signal φTX is supplied to the first transfer MOS transistor M1. As a result, the first transfer MOS transistor M1 is turned on, and the charge accumulated in the photodiode PD is transferred to the floating diffusion region FD. As will be described later, in this embodiment, a signal of 5 [V] is used as the high-level control signal φTX.

  At time t8, the low-level control signal φTX is supplied to the first transfer MOS transistor M1. As a result, the first transfer MOS transistor M1 is turned off, and the transfer operation of the charge accumulated in the photodiode PD is completed. When this transfer operation is performed, the read level (N1) in the floating diffusion region FD and the signal level (S1) based on the charges accumulated in the floating diffusion region FD are read out. As will be described later, in the present embodiment, a signal of −1 [V] is used as the low-level control signal φTX.

At time t9, a high level control signal φTX is supplied to the first transfer MOS transistor M1, and a high level control signal φS is supplied to the second transfer MOS transistor M3. As a result, the first transfer MOS transistor M1 and the second transfer MOS transistor M3 are turned on. By this operation, the signal level (S1) based on the charge accumulated in the floating diffusion region FD, the signal level (S2) based on the charge accumulated in the additional capacitor CS, and the reset level (N1) in the floating diffusion region FD The reset level (N2 ′) of the same amount as the reset level in the floating diffusion region FD and the additional capacitor CS is added and read.
Finally, at time t10, the low-level control signal φTX is supplied to the first transfer MOS transistor M1, and the first transfer MOS transistor M1 is turned off to complete one cycle of operation.

As described above, in this embodiment, at time t3 to t4, at least a part of the electric charge overflowing from the photodiode PD is caused to flow into the floating diffusion region FD via the path 31 shown in FIG. Hereinafter, the path 31 of the present embodiment will be described with reference to FIGS. 3 and 4.
FIG. 3 is a plan view illustrating an example of a schematic configuration of the pixel of the present embodiment. Note that FIG. 3 shows a configuration for 2 × 2 pixels. It goes without saying that the pixels of the solid-state imaging device of the present embodiment are not limited to four pixels.

  In FIG. 3, reference numerals 21a to 21d denote photodiodes corresponding to the photodiode FD of FIG. Reference numerals 22a to 22d denote first transfer MOS transistors, which correspond to the first transfer MOS transistor M1 in FIG. Reference numerals 23a to 23d denote floating diffusion regions, which correspond to the floating diffusion region FD in FIG.

  Reference numeral 24 denotes a P-type layer for forming a potential barrier. Reference numerals 25a to 25d denote element groups other than the photodiodes 21a to 21d and the first transfer MOS transistors 22a to 22d. Specifically, the element groups 25a to 25d include the reset MOS transistor M2, the second transfer MOS transistor M3, the source follower MOS transistor M4, the selection MOS transistor M5, and the additional capacitor CS shown in FIG. Further, a region indicated by a thick line in FIG. 3 indicates a diffusion layer (N + layer) in each element.

  In the present embodiment, the photodiodes 21a to 21d, the first transfer MOS transistors 22a to 22d, and the element groups 25a to 25d are formed on a P-type well (P well).

  The potential barrier forming P-type layer 24 is a layer containing a P-type impurity at a higher concentration than the P well. The P-type layer 24 for potential barrier formation, which is such a high-concentration P-type region, is formed in a region in the P-well excluding the lower side of the gates of the first transfer MOS transistors 22a to 22d. However, the P-type layer 24 for forming the potential barrier does not need to be formed over the entire depth direction of the P well, and the potential barrier is formed in a region deeper than the region necessary for forming the path 31. The P-type layer 24 may not be formed.

  FIG. 4 is a diagram showing the pixels viewed from the direction AB in FIG. 3 in a simplified manner. FIG. 4A is a diagram schematically illustrating the state of the pixel viewed from the AB direction in FIG. 3 and the potential distribution in the depth direction of the pixel. FIG. 4B is a diagram showing the potential at the time of charge accumulation at a predetermined position in the path 31. FIG. 4C is a diagram showing the potential at the time of charge transfer at a predetermined position in the path 31.

  4A, in this embodiment, as the potential barrier forming P-type layer 24, the channel stop region having the first concentration (and this channel stop region may also be used as the potential barrier forming P-type layer). .) 24a, a second potential barrier forming P-type layer 24b having a second concentration, and a third potential barrier forming P-type layer 24c having a third concentration. ing.

  In the present embodiment, the P-type impurity concentration in the second potential barrier forming P-type layer 24b is set to be the first potential barrier forming P-type layer 24b formed above and below the second potential barrier forming P-type layer 24b. It is lower than the P-type layer 24a and the third potential barrier forming P-type layer 24c. In this case, as shown in FIG. 4A, the region where the second potential barrier forming P-type layer 24b is formed in the region below the gates of the first transfer MOS transistors 22a to 22d. The potential of the region at the same depth as can be made the lowest. Thus, in this embodiment, the potential in the path 31 can be adjusted by changing the concentration in the depth direction of the second potential barrier forming P-type layer 24b.

  Specifically, the path 31 is formed at a position deeper than the channel formed between the source and drain of the first transfer MOS transistors 22a to 22d (that is, below the channel). In this case, it is preferable to form the path 31 as deep as possible so as not to be affected by the gate potentials of the first transfer MOS transistors 22a to 22d. However, as described above, the path 31 flows in the charges overflowing from the photodiode 21. For this reason, the path 31 needs to be formed at a position shallower than the lower end of the photodiode 21.

  When charges are accumulated in the photodiode 21 or the floating diffusion region 23, the potential (gate potential) Vg at the gate of the first transfer MOS transistor 22, the potential OFD of the path 31, the potential PD of the photodiode 21, the floating diffusion The potential FD in the region 23 and the potential AP in the region (P-type layer 24 for potential barrier formation) in the lateral direction (AB direction in FIG. 3) of the path 31 are given as shown in FIG. .

  As shown in FIG. 4, by forming the potential barrier forming P-type layer 24, the potential OFD of the path 31 below the gate of the first transfer MOS transistor 22 can be lowered. As a result, the charge overflowing from the photodiode 21 during the charge accumulation operation in the photodiode 21 can flow into the path 31.

  As described above, in the present embodiment, the potential barrier forming P-type layer 24 is formed in the region in the P well excluding the region below the gate of the first MOS transistor 22. Accordingly, when the charge is accumulated, the gate potential Vg of the first transfer MOS transistor 22 is set to −1 [V] and the potential in the region immediately below the gate of the first transfer MOS transistor 22 is increased ( Even if the first transfer MOS transistor 22 is turned off as reliably as possible, the charge overflowing from the photodiode 21 can flow into the path 31. This prevents the region immediately below the gate of the first transfer MOS transistor 22 from becoming a depletion region, and allows dark current to be generated from the interface of the gate oxide film 41 of the first transfer MOS transistor 22. It is possible to simultaneously realize prevention and expansion of the dynamic range of the solid-state imaging device using the electric charge accumulated in the floating diffusion region FD via the path 31.

  On the other hand, when transferring charges from the photodiode 21, the gate potential Vg of the first transfer MOS transistor 22, the potential OFD in the path 31, the potential PD of the photodiode 21, the potential FD in the floating diffusion region 23, and the path 31. The potential AP in the horizontal region (potential barrier forming P-type layer 24) is given as shown in FIG.

  As described above, when transferring charges, the gate potential Vg of the first transfer MOS transistor 22 is set to 5 [V], and the potential in the region (channel region) immediately below the gate of the first transfer MOS transistor 22 is set. Is trying to lower. Thereby, the charge accumulated in the photodiode 21 can be reliably transferred to the floating diffusion region 23.

In the present embodiment, the gate potential Vg of the first transfer MOS transistor 22 during charge accumulation is set to -1 [V], and the gate potential Vg of the first transfer MOS transistor 22 during charge transfer is set to -1 [V]. However, it goes without saying that the gate potential Vg of the first transfer MOS transistor 22 is not limited to these.
In addition, if the second transfer MOS transistor M3 and the additional capacitor CS are used as in the present embodiment, the dynamic range of the solid-state imaging device can be further expanded. However, the second transfer MOS transistor M3 is not necessarily used. It is not necessary to use the additional capacitor CS.

Furthermore, in the present embodiment, the P-type layer 24 for forming the potential barrier is provided, but the P-type impurity concentration in the path 31 is relatively higher than that in the region in the horizontal direction (AB direction in FIG. 3) of the path 31. If the potential is lower (if the potential in the path 31 is made lower than the region in the side direction of the path 31 (A-B direction in FIG. 3)), the potential barrier forming P-type layer 24 is not necessarily used. There is no need to provide. For example, an n-type impurity may be added at a position where the path 31 in FIG.
Further, the formation region of the P-type layer 24 for forming the potential barrier may be formed including the lower region of the transistor, or is formed so as to cover at least the region where the photodiode PD is formed as shown in FIG. May be.

(Other embodiments)
Based on FIG. 6, one embodiment when the solid-state imaging device of the above-described embodiment is applied to a still camera will be described in detail.
FIG. 6 is a block diagram showing a case where the solid-state imaging device of the above-described embodiment is applied to a “still video camera”.
In FIG. 6, reference numeral 1301 denotes a barrier that serves both as lens protection and a main switch, reference numeral 1302 denotes a lens that forms an optical image of a subject on the solid-state imaging device 1304, and reference numeral 1303 denotes a variable amount of light passing through the lens 1302. 1304 is a solid-state imaging device for capturing the subject imaged by the lens 1302 as an image signal, and 1306 is an analog-digital conversion of the image signal output from the solid-state imaging device 1304. An A / D converter to perform.

  A signal processing unit 1307 performs various corrections on the image data output from the A / D converter 1306 and compresses the data. 1308 denotes a solid-state imaging device 1304, an imaging signal processing circuit 1305, and an A / D. A timing generator that outputs various timing signals to the D converter 1306 and the signal processor 1307, 1309 is an overall control / arithmetic unit that controls various calculations and the entire still video camera, and 1310 is image data. Is a memory unit for temporarily storing data, 1311 is an interface unit for recording or reading data on a recording medium, and 1312 is a detachable semiconductor memory for recording or reading image data. Reference numeral 1313 denotes an interface unit for communicating with an external computer or the like.

Next, the operation of the still video camera at the time of shooting in the above configuration will be described.
When the barrier 1301 is opened, the main power supply is turned on, then the control system power supply is turned on, and the power supply of the imaging system circuit such as the A / D converter 1306 is turned on.
Then, in order to control the exposure amount, the overall control / arithmetic unit 1309 opens the aperture 1303, and the signal output from the solid-state imaging device 1304 is converted by the A / D converter 1306 and then sent to the signal processing unit 1307. Entered.
Based on the data, the exposure control is performed by the overall control / calculation unit 1309.
The brightness is determined based on the result of the photometry, and the overall control / calculation unit 1309 controls the aperture according to the result.

Based on the signal output from the solid-state imaging device 1304, the high-frequency component is extracted and the distance to the subject is calculated by the overall control / calculation unit 1309. Thereafter, the lens is driven to determine whether or not it is in focus. When it is determined that the lens is not in focus, the lens is driven again to perform distance measurement.
Then, after the in-focus state is confirmed, the main exposure starts.
When the exposure is completed, the image signal output from the solid-state imaging device 1304 is A / D converted by the A / D converter 1306, passes through the signal processing unit 1307, and is written in the memory unit by the overall control / calculation unit 1309.

  Thereafter, the data stored in the memory unit 1310 is recorded on a removable recording medium 1312 such as a semiconductor memory through the recording medium control I / F unit under the control of the overall control / arithmetic unit 1309. Further, the image may be processed by directly inputting to a computer or the like through the external I / F unit 1313.

Next, an example when the solid-state imaging device of the above-described embodiment is applied to a video camera will be described in detail with reference to FIG.
FIG. 7 is a block diagram showing a case where the solid-state imaging device of the above-described embodiment is applied to a “video camera”. In FIG. 7, reference numeral 1401 denotes a photographing lens, which includes a focus lens 1401A for performing focus adjustment, a zoom lens 1401B for performing a zoom operation, and an imaging lens 1401C.
1402 is a stop, 1403 is a solid-state image sensor that photoelectrically converts an object image formed on the imaging surface into an electrical image signal, and 1404 is an image signal output from the solid-state image sensor 3. Is a sample hold circuit (S / H circuit) that further amplifies the level and outputs a video signal.

  Reference numeral 1405 denotes a process circuit that performs predetermined processing such as gamma correction, color separation, and blanking processing on the video signal output from the sample hold circuit 1404, and outputs a luminance signal Y and a chroma signal C. The chroma signal C output from the process circuit 1405 is subjected to white balance and color balance correction by a color signal correction circuit 1421 and is output as color difference signals RY and BY.

In addition, the luminance signal Y output from the process circuit 1405 and the color difference signals RY and BY output from the color signal correction circuit 1421 are modulated by an encoder circuit (ENC circuit) 1424 to be a standard television signal. Is output as Then, it is supplied to a video recorder (not shown) or an electronic viewfinder such as a monitor EVF (Electric View Finder).
Reference numeral 1406 denotes an iris control circuit which controls the iris driving circuit 1407 based on the video signal supplied from the sample hold circuit 1404, and sets the aperture of the diaphragm 1402 so that the level of the video signal becomes a predetermined value. The ig meter is automatically controlled to be controlled.

Reference numerals 1413 and 1414 denote different band-limited band pass filters (BPF) for extracting high-frequency components necessary for performing focus detection from the video signal output from the sample hold circuit 1404. The signals output from the first bandpass filter 1413 (BPF1) and the second bandpass filter 1414 (BPF2) are gated by the gate circuit 1415 and the focus gate frame signal, respectively, and the peak value is obtained by the peak detection circuit 1416. It is detected and held and input to the logic control circuit 1417.
This signal is called a focus voltage, and the focus is adjusted by this focus voltage.

Reference numeral 1418 denotes a focus encoder that detects the moving position of the focus lens 1401A, 1419 denotes a zoom encoder that detects the focal length of the zoom lens 1401B, and 1420 denotes an iris encoder that detects the opening amount of the aperture 1402. The detection values of these encoders are supplied to a logic control circuit 1417 that performs system control.
The logic control circuit 1417 performs focus detection on the subject based on a video signal corresponding to the set focus detection area, and performs focus adjustment. That is, the high-frequency component peak value information supplied from each of the bandpass filters 1413 and 1414 is taken in, and the focus driving circuit 1409 is driven to the focus motor 1410 to drive the focus lens 1401A to the position where the peak value of the high-frequency component is maximized. Control signals such as a rotation direction, a rotation speed, and rotation / stop are supplied and controlled.

  It should be noted that each of the above-described embodiments is merely an example of realization of the present invention, and the technical scope of the present invention should not be construed in a limited manner. .

CS additional capacitor M2 reset MOS transistor M3 second transfer MOS transistor M4 source follower MOS transistor M5 selection MOS transistor 21, PD photodiode 22, M1 first transfer MOS transistor 23, FD floating diffusion region 24 P type for potential barrier formation Layer 31 pathway

Claims (11)

A photoelectric conversion unit that generates charges by incident light; and
A charge accumulation region for accumulating charges generated by the photoelectric conversion unit;
A first transfer MOS transistor disposed between the photoelectric conversion unit and the charge storage region for transferring the charge generated by the photoelectric conversion unit to the charge storage region;
A path different from the channel of the first transfer MOS transistor, and a path when a part of the charge overflowing from the photoelectric conversion unit moves to the charge accumulation region;
An additional capacitor for accumulating a part of the electric charge overflowing from the photoelectric conversion unit;
A second transfer MOS transistor disposed between the charge storage region and the additional capacitor for transferring the charge stored in the additional capacitor to the charge storage region;
A potential barrier layer for the charge is disposed in the first conductivity type well;
The potential barrier layer is provided in the well except under the gate electrode of the first transfer MOS transistor, and is a first conductivity type region having a higher impurity concentration of the first conductivity type than the well;
The impurity concentration of the first conductivity type in the path is lower than the impurity concentration of the first conductivity type of the potential barrier layer,
The path is located deeper in the well than the region where the channel of the first transfer MOS transistor is formed, and the width of the path in the cross-section in the width direction of the gate electrode of the first transfer MOS transistor so as to be sandwiched between the potential barrier layer in the direction, the solid-state imaging device according to claim that you have located between the potential barrier layer.   The accumulation operation in which charges are accumulated in the additional capacitor when the first transfer MOS transistor is off and the second transfer MOS transistor is on ends when the second transfer MOS transistor is turned off. The solid-state imaging device according to claim 1.   The solid-state imaging device according to claim 1, wherein an image signal is generated using a signal based on the charge accumulated in the additional capacitor.   The charge generated in the photoelectric conversion unit is transferred to the charge storage region when the first transfer MOS transistor is turned on while the second transfer MOS transistor is turned off. Item 4. The solid-state imaging device according to any one of Items 1 to 3.   When the first transfer MOS transistor and the second transfer MOS transistor are turned on, a signal level based on the charge accumulated in the charge accumulation region, a signal level based on the charge accumulated in the additional capacitor, 5. The read level according to claim 1, wherein the reset level in the charge accumulation region and the reset level substantially equal to the reset level in the charge accumulation region and the additional capacitor are added and read. Solid-state imaging device.   The gate potential of the first transfer MOS transistor when the first transfer MOS transfer transistor is off is a negative value. 6. Solid-state imaging device. The solid-state imaging device according to claim 1, wherein the charge accumulation region is a floating diffusion region. The photoelectric conversion unit includes a second conductivity type semiconductor region disposed in the well and capable of storing the charge, and the path is at a position shallower than a lower end of the second conductivity type semiconductor region. It forms, The solid-state imaging device of any one of Claims 1-7 characterized by the above-mentioned. The solid-state imaging device according to claim 1, wherein the path is a first conductivity type region. The solid-state imaging device according to claim 1, wherein the potential barrier layer has a different concentration in a depth direction. A solid-state imaging device according to any one of claims 1 to 10 ,
A lens for forming an optical image on the solid-state imaging device;
And a diaphragm for varying the amount of light passing through the lens.

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