Patent Publication Number: US-2023154943-A1

Title: Photoelectric conversion device and light emitting device

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to a photoelectric conversion device and a light emitting device. 
     Description of the Related Art 
     Japanese Patent Application Laid-Open No. 2016-5068 discloses a solid-state imaging device including an amplifying transistor for reading out a signal corresponding to a charge accumulated in a photoelectric conversion unit. Japanese Patent Application Laid-Open No. 2016-5068 discloses a technology for realizing high frame rate photographing by connecting a plurality of amplifying transistors in parallel to increase transconductance. 
     In a device having a transistor, an increase in transconductance of the transistor may be desired to improve performance. As an example of such a method, there is a method of connecting a plurality of transistors in parallel as described in Japanese Patent Application Laid-Open No. 2016-5068, but there are cases where it is not appropriate to apply this method. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present disclosure is to provide a photoelectric conversion device and a light emitting device with improved performance. 
     According to an aspect of the present disclosure, there is provided a photoelectric conversion device including a substrate, a photoelectric conversion unit configured to generate charges corresponding to incident light, a floating diffusion portion to which the charges generated by the photoelectric conversion unit are transferred, and a transistor arranged in the substrate, the transistor having a plurality of main electrodes and a gate connected to the floating diffusion portion, the transistor being configured to output a signal corresponding to a potential of the floating diffusion portion from at least one of the plurality of main electrodes. In a plan view with respect to the substrate, the gate has four or more sides. In the plan view, the plurality of main electrodes is adjacent to three or more sides of the gate. 
     According to another aspect of the present disclosure, there is provided a light emitting device including a substrate, a light emitting element, and a transistor arranged in the substrate, the transistor having a plurality of main electrodes and a gate, the transistor being configured to supply a current corresponding to a potential of the gate from at least one of the plurality of main electrodes to the light emitting element. In a plan view with respect to the substrate, the gate has four or more sides. In the plan view, the plurality of main electrodes is adjacent to three or more sides of the gate. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a block diagram illustrating a schematic configuration of a photoelectric conversion device according to a first embodiment. 
         FIG.  2    is an equivalent circuit diagram of a pixel according to the first embodiment. 
         FIG.  3    is a schematic plan view of the pixel according to the first embodiment. 
         FIG.  4    is a schematic plan view of an amplifying transistor according to the first embodiment. 
         FIG.  5    is a schematic plan view of an amplifying transistor according to a modified example of the first embodiment. 
         FIG.  6    is a schematic plan view of an amplifying transistor according to another modified example of the first embodiment. 
         FIG.  7    is a schematic plan view of an amplifying transistor according to another modified example of the first embodiment. 
         FIG.  8    is a schematic plan view of an amplifying transistor according to another modified example of the first embodiment. 
         FIG.  9    is a schematic plan view of an amplifying transistor according to another modified example of the first embodiment. 
         FIG.  10    is a schematic plan view of an amplifying transistor according to another modified example of the first embodiment. 
         FIG.  11    is an equivalent circuit diagram of a pixel according to a second embodiment. 
         FIG.  12    is a schematic plan view of the pixel according to the second embodiment. 
         FIG.  13    is a block diagram of equipment according to a third embodiment. 
         FIGS.  14 A and  14 B  are block diagrams of equipment according to a fourth embodiment. 
         FIG.  15    is an equivalent circuit diagram of a pixel of the light emitting device according to a fifth embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. In the drawings, the same or corresponding elements are denoted by the same reference numerals, and the description thereof may be omitted or simplified. 
     In first and second embodiments described below, an imaging device will be mainly described as an example of a photoelectric conversion device. However, the photoelectric conversion device of each embodiment is not limited to the imaging device, and can be applied to other devices. Examples of other devices include a ranging device and a photometry device. The ranging device may be, for example, a focus detection device, a distance measuring device using a time-of-flight (TOF), or the like. The photometric device may be a device for measuring an amount of light incident on the device. 
     First Embodiment 
       FIG.  1    is a block diagram illustrating a schematic configuration of a photoelectric conversion device according to the present embodiment. The photoelectric conversion device of the present embodiment includes a pixel array  100 , a vertical scanning circuit  101 , a column reading circuit  102 , a horizontal scanning circuit  103 , an output circuit  104 , and a control circuit  105 . The circuit constituting the photoelectric conversion device may be formed in one or a plurality of semiconductor substrates. 
     The pixel array  100  includes a plurality of pixels  20  arranged in a plurality of rows and a plurality of columns. Each of the plurality of pixels  20  generates charges by photoelectrically converting incident light and outputs a signal corresponding to the incident light. Microlenses and color filters may be arranged on the pixels  20 . 
     In each row of the pixel array  100 , a plurality of control lines  30  are arranged so as to extend in the first direction (x-direction in  FIG.  1   ). Each of the plurality of control lines  30  is connected to the pixels  20  arranged in the first direction, and serves as a signal line common to the pixels  20 . The first direction in which the control lines  30  extend may be referred to as a row direction or a horizontal direction. The control lines  30  are connected to the vertical scanning circuit  101 . 
     In each column of the pixel array  100 , output lines  40  are arranged so as to extend in a second direction (y-direction in  FIG.  1   ) intersecting with the first direction. Each of the output lines  40  is connected to the pixels  20  arranged in the second direction, and serves as a signal line common to the pixels  20 . The second direction in which the output lines  40  extend may be referred to as a column direction or a vertical direction. Each of the output lines  40  is connected to a current source  41 , which will be described later with reference to  FIG.  2   , and the column reading circuit  102 . 
     The control circuit  105  outputs control signals such as a vertical synchronization signal, a horizontal synchronization signal, and a clock signal to the vertical scanning circuit  101 , the column reading circuit  102 , and the horizontal scanning circuit  103 . Thus, the control circuit  105  controls the operation of these circuits. 
     The vertical scanning circuit  101  is a scanning circuit including logic circuits such as a shift register, a gate circuit, and a buffer circuit. The vertical scanning circuit  101  outputs a control signal to the pixels  20  via the control lines  30  based on a vertical synchronization signal, a horizontal synchronization signal, a clock signal, and the like, and performs scanning for sequentially outputting signals from the pixels  20  on a row basis. The vertical scanning circuit  101  controls a charge accumulation period in the pixels  20 . 
     The signal generated by the pixel  20  is output to the column reading circuit  102  via the output line  40  on a corresponding column. The column reading circuit  102  includes column circuits corresponding to respective columns. The column circuit performs processing such as amplification and AD conversion on the signal input through the output line  40 , and holds the processed signal on a column basis. 
     The horizontal scanning circuit  103  is a scanning circuit including logic circuits such as a shift register, a gate circuit, and a buffer circuit. The horizontal scanning circuit  103  sequentially selects a plurality of column circuits of the column reading circuit  102 . Thus, each of the plurality of column circuits sequentially outputs the held signals to the output circuit  104 . The output circuit  104  outputs signals to the outside of the photoelectric conversion device in a predetermined format. 
       FIG.  2    is an equivalent circuit diagram of the pixel  20  according to the present embodiment. In the following description, it is assumed that the charges accumulated in the photoelectric conversion unit in the pixel  20  are electrons. All the transistors included in the pixel  20  are N-type MOS transistors. However, the charges accumulated in the photoelectric conversion unit may be holes, and in this case, the transistors in the pixel  20  may be P-type MOS transistors. That is, the conductivity type of the transistors or the like can be changed as appropriate depending on the polarity of charges handled as a signal. 
     The pixel  20  includes a photoelectric conversion unit PD, a transfer transistor M 1 , a reset transistor M 2 , an amplifying transistor M 3 , and a selection transistor M 4 . The photoelectric conversion unit PD is, for example, a photodiode. The anode of the photoelectric conversion unit PD is connected to a ground node, and the cathode of the photoelectric conversion unit PD is connected to the source of the transfer transistor M 1 . The drain of the transfer transistor M 1  is connected to the source of the reset transistor M 2  and the gate of the amplifying transistor M 3 . A node to which the drain of the transfer transistor M 1 , the source of the reset transistor M 2 , and the gate of the amplifying transistor M 3  are connected is a floating diffusion portion FD. The floating diffusion portion FD has a capacitance component (floating diffusion capacitance) and functions as a charge holding portion. The floating diffusion capacitance includes parasitic capacitance in an electrical path from the transfer transistor M 1  to the amplifying transistor M 3  via the floating diffusion portion FD. 
     The drain of the reset transistor M 2  and the drain of the amplifying transistor M 3  are connected to a power supply voltage node to which a voltage VDD is supplied. The source of the amplifying transistor M 3  is connected to the drain of the selection transistor M 4 . The source of the selection transistor M 4  is connected to the output line  40 . 
     A current source  41  is connected to the output line  40 . The current source  41  may be a current source whose current value can be switched or a constant current source whose current value is constant. 
     In the case of the pixel configuration of  FIG.  2   , the control lines  30  of each row includes a signal line connected to the gate of the transfer transistor M 1 , a signal line connected to the gate of the reset transistor M 2 , and a signal line connected to the gate of the selection transistor M 4 . A control signal pTX is supplied from the vertical scanning circuit  101  to the gate of the transfer transistor M 1 . A control signal pRES is supplied from the vertical scanning circuit  101  to the gate of the reset transistor M 2 . A control signal pSEL is supplied from the vertical scanning circuit  101  to the gate of the selection transistor M 4 . A plurality of pixels  20  in the same row are connected to a common signal line, and are controlled simultaneously by a common control signal. 
     In the present embodiment, each transistor constituting the pixel  20  is an N-type MOS transistor. Therefore, when a high-level control signal is supplied from the vertical scanning circuit  101 , the corresponding transistor is turned on. When a low-level control signal is supplied from the vertical scanning circuit  101 , the corresponding transistor is turned off. The terms “source” and “drain” of the MOS transistor may vary depending on the conductivity type of the transistor or the target function. Some or all of the names of “source” and “drain” used in this embodiment may be referred to by the opposite names. 
     The photoelectric conversion unit PD converts (photoelectrically converts) incident light into charges corresponding to the amount of the incident light. The transfer transistor M 1  is turned on to transfer charges held in the photoelectric conversion unit PD to the floating diffusion portion FD. The charges transferred from the photoelectric conversion unit PD is held in the capacitance (floating diffusion capacitance) of the floating diffusion portion FD. As a result, the floating diffusion portion FD has a potential corresponding to the amount of charges transferred from the photoelectric conversion unit PD by charge-to-voltage conversion by the floating diffusion capacitance. 
     The selection transistor M 4  is turned on to connect the amplifying transistor M 3  to the output line  40 . The amplifying transistor M 3  is configured such that a voltage VDD is supplied to the drain of the amplifying transistor M 3  and a bias current is supplied from the current source  41  to the source of the amplifying transistor M 3  via the selection transistor M 4 , and constitutes an amplifying unit (source follower circuit). The gate of the amplifying transistor M 3  functions as an input node of the amplifying unit. Accordingly, the amplifying transistor M 3  outputs a signal based on the potential of the floating diffusion portion FD to the output line  40  through the selection transistor M 4 . In this sense, the amplifying transistor M 3  and the selection transistor M 4  are an output unit that outputs a pixel signal corresponding to the amount of charges held in the floating diffusion portion FD. 
     The reset transistor M 2  has a function of resetting the floating diffusion portion FD by controlling supply of a voltage (voltage VDD) to the floating diffusion portion FD. When the reset transistor M 2  is turned on, the floating diffusion portion FD is reset to a voltage corresponding to the voltage VDD. 
     Although  FIG.  2    illustrates a configuration in which a signal is output to the corresponding output line  40  through one selection transistor M 4 , the configuration of the selection transistor M 4  and the output line  40  is not limited thereto. For example, in a configuration in which a plurality of selection transistors M 4  and a plurality of output lines  40  are arranged for one pixel  20 , a configuration may be adopted in which the output line  40  for outputting a signal can be selected by individually controlling the plurality of selection transistors M 4 . 
       FIG.  3    is a schematic plan view of the pixel  20  according to the present embodiment.  FIG.  3    illustrates an arrangement of the photoelectric conversion unit PD, the floating diffusion portion FD, and the gate, source, and drain of each transistor in a plan view with respect to the substrate. The gates  21 ,  22 ,  23 , and  24  illustrated in  FIG.  3    indicates an arrangement of the gate electrodes of the transfer transistor M 1 , the reset transistor M 2 , the amplifying transistor M 3 , and the selection transistor M 4 , respectively. 
     As illustrated in  FIG.  3   , the photoelectric conversion unit PD is arranged near the center of the pixel  20 . The floating diffusion portion FD is arranged outside the photoelectric conversion unit PD, and the gate  21  is arranged between the photoelectric conversion unit PD and the floating diffusion portion FD. The gates  22 ,  23 , and  24  are arranged side by side on the side opposite to the floating diffusion portion FD with respect to the photoelectric conversion unit PD. 
     In the layout of  FIG.  3   , the amplifying transistor M 3  and the selection transistor M 4  are formed in the same active region, but the layout is not limited thereto. An element isolation region is formed between the plurality of active regions. 
       FIG.  4    is a schematic plan view of the amplifying transistor M 3  according to the present embodiment. In other words,  FIG.  4    is an enlarged view of the amplifying transistor M 3  in  FIG.  3   . The amplifying transistor M 3  has one gate  23 , one drain  25 , and two sources  26   a  and  26   b . As illustrated in  FIG.  4   , the gate  23  has a quadrangular shape having four sides S 1 , S 2 , S 3 , and S 4 . The drain  25  is adjacent to the side S 3 . The source  26   a  is adjacent to the side S 2 , and the source  26   b  is adjacent to the side S 4 . Thus, the sources  26   a  and  26   b  are adjacent to the two sides S 2  and S 4  opposed to each other, and the drain  25  is adjacent to the side S 3  that is not opposed to the sides S 2  and S 4 . As described above, in the present embodiment, the amplifying transistor M 3  has nodes of the two sources  26   a  and  26   b  for one gate  23 . The nodes of the two sources  26   a  and  26   b  may be electrically connected via, for example, a contact plug and a metal wiring. However, the nodes of the two sources  26   a ,  26   b  may be electrically independent. 
     As described above, in the amplifying transistor M 3  of the present embodiment, the gate  23  has the four sides S 1 , S 2 , S 3 , and S 4  in the plan view. A plurality of main electrodes including the two sources  26   a  and  26   b  (a plurality of first main electrodes) and the drain  25  (a second main electrode) are adjacent to the three sides S 2 , S 3 , and S 4  of the gate  23 . The effect of the amplifying transistor M 3  having such a configuration will be described below. 
     In order to realize high frame rate photographing, it is required to speed up the operation of the amplifying transistor M 3 . One of the methods for achieving high speed is to increase the transconductance gm of the amplifying transistor M 3 . The transconductance gm of the amplifying transistor M 3  is increased by shortening the gate length L or widening the gate width W. 
     In general, the random noise of the amplifying transistor M 3  is inversely proportional to the product of the gate length L and the gate width W of the amplifying transistor M 3 . Therefore, when the gate length L of the amplifying transistor M 3  is shortened, the random noise of the amplifying transistor M 3  increases. 
     On the other hand, when the gate width W of the amplifying transistor M 3  is widened, the area of the region of the photoelectric conversion unit PD arranged in the vicinity of the amplifying transistor M 3  may need to be reduced in order to secure the area of the gate  23 , thereby reducing the saturation signal amount of the pixel  20 . 
     Thus, when the gate length L of the amplifying transistor M 3  is shortened or the gate width W is widened in order to increase the transconductance gm, the quality of the output signal may deteriorate. 
     On the other hand, in the present embodiment, the two sources  26   a  and  26   b  of the amplifying transistor M 3  are adjacent to the two sides S 2  and S 4  of the gate  23 . Thus, by arranging the sources  26   a  and  26   b  on two or more sides of the gate  23 , a state equivalent to a state in which the gate width W of the amplifying transistor M 3  is widened is realized. This increases transconductance gm. However, from the viewpoint of the actual dimension of the gate  23  of the amplifying transistor M 3 , since neither the shortening of the gate length L nor the widening of the gate width W is performed, the degradation of the signal quality as described above is less likely to occur. As described above, since a state in which the actual dimension is not changed while effectively widening the gate width W of the amplifying transistor M 3  is realized, it is possible to achieve both the signal quality and the transconductance gm. Therefore, according to the present embodiment, it is possible to provide a photoelectric conversion device with improved performance. 
     As one method for increasing the S/N ratio of the photoelectric conversion device, there is a method in which the parasitic capacitance of the floating diffusion portion FD is reduced to improve photoelectric conversion efficiency, and random noise superimposed on an output signal is reduced. Therefore, the parasitic capacitance of the floating diffusion portion FD is desirably reduced from the viewpoint of improving the S/N ratio by reducing random noise. 
     As another method of increasing the transconductance gm of the amplifying transistor, a method of widening the gate width W of the amplifying transistor or a method of connecting a plurality of amplifying transistors in parallel may be considered. When these methods are adopted, parasitic capacitance generated between the floating diffusion portion FD and the gate  23  of the amplifying transistor M 3  may be large. When the capacitance of the floating diffusion portion FD increases due to the parasitic capacitance, the photoelectric conversion efficiency decreases, and the random noise superimposed on the output signal may increase. 
     On the other hand, in the photoelectric conversion device of the present embodiment, the drain  25  is adjacent to only one side of the gate  23 , and a state equivalent to a state in which the gate width W of the drain  25  of the amplifying transistor M 3  is effectively narrowed is realized. Thus, parasitic capacitance between the power supply voltage node to which the voltage VDD (power supply potential) is supplied and the gate  23  of the amplifying transistor M 3  can be reduced. Therefore, since the capacitance of the floating diffusion portion FD is reduced and the photoelectric conversion efficiency is improved, the effect of reducing the random noise superimposed on the output signal is obtained. 
     The layout of the amplifying transistor M 3  is not limited to that illustrated in  FIGS.  3  and  4   . Hereinafter, a modified example of the layout of the amplifying transistor M 3  will be described with reference to  FIGS.  5  to  10   . 
       FIG.  5    is a schematic plan view of an amplifying transistor M 3  according to a modification of the present embodiment. The amplifying transistor M 3  has one gate  23 , one drain  25 , and two sources  26   a  and  26   b . As illustrated in  FIG.  5   , the gate  23  has a quadrangular shape having four sides S 1 , S 2 , S 3 , and S 4 . The drain  25  is adjacent to the side S 3 . The source  26   a  is adjacent to the side S 2 , and the source  26   b  is adjacent to the side S 1 . Thus, the sources  26   a  and  26   b  are adjacent to the two sides S 2  and S 1  that are not opposed to each other, and the drain  25  is adjacent to the side S 3  that is opposed to the side S 1 . As described above, also in this modification, the amplifying transistor M 3  has nodes of the two sources  26   a  and  26   b  for one gate  23 . The nodes of the two sources  26   a  and  26   b  may be electrically connected via, for example, a contact plug and a metal wiring. However, the nodes of the two sources  26   a ,  26   b  may be electrically independent. Also in this modification, the same effect as the configuration illustrated in  FIG.  4    can be obtained. Thus, the positions of the sides of the gate  23  adjacent to the two sources  26   a  and  26   b  are not limited to that illustrated in  FIG.  4   . 
       FIG.  6    is a schematic plan view of an amplifying transistor M 3  according to another modification of the present embodiment. The amplifying transistor M 3  has one gate  23 , one drain  25 , and one source  26 . As illustrated in  FIG.  6   , the gate  23  has a quadrangular shape having four sides S 1 , S 2 , S 3 , and S 4 . The drain  25  is adjacent to the side S 3 . The source  26  is adjacent to the side S 1  and the side S 2 . Thus, the source  26  is adjacent to the two sides S 1  and S 2  that are not opposed to each other, and the drain  25  is adjacent to the side S 3  that is opposed to the side S 1  and not opposed to the side S 2 . As described above, in this modification, the amplifying transistor M 3  has a node of the source  26  adjacent to one gate  23  on two sides. Also in this modification, the same effect as the configuration illustrated in  FIG.  4    can be obtained. As described above, in the amplifying transistor M 3  of the present embodiment, one source  26  may be adjacent to two or more sides of the gate  23 . 
       FIG.  7    is a schematic plan view of an amplifying transistor M 3  according to another modification of the present embodiment. The amplifying transistor M 3  has one gate  23 , one drain  25 , and three sources  26   a ,  26   b , and  26   c . As illustrated in  FIG.  7   , the gate  23  has a quadrangular shape having four sides S 1 , S 2 , S 3 , and S 4 . The drain  25  is adjacent to the side S 3 . The source  26   a  is adjacent to the side S 2 , the source  26   b  is adjacent to the side S 4 , and the source  26   c  is adjacent to the side S 1 . Thus, the sources  26   a  and  26   b  are adjacent to the two sides S 2  and S 4  opposed to each other, and the source  26   c  is adjacent to the side S 1  not opposed to those sides. The drain  25  is adjacent to the side S 3  opposed to the side S 1 . As described above, in this modification, the amplifying transistor M 3  has three nodes of the sources  26   a ,  26   b , and  26   c  for one gate  23 . The nodes of the three sources  26   a ,  26   b , and  26   c  may be electrically connected via, for example, a contact plug and a metal wiring. However, the nodes of the two sources  26   a ,  26   b  may be electrically independent. Also in this modification, the same effect as the configuration illustrated in  FIG.  4    can be obtained. Thus, the number of sides of the gate  23  adjacent to the source is not limited to two as illustrated in  FIG.  4   , and may be three or more. 
       FIG.  8    is a schematic plan view of an amplifying transistor M 3  according to another modification of the present embodiment. The amplifying transistor M 3  has one gate  23 , one drain  25 , and one source  26 . As illustrated in  FIG.  8   , the gate  23  has a quadrangular shape having four sides S 1 , S 2 , S 3 , and S 4 . The drain  25  is adjacent to the side S 3 . The source  26  is adjacent to the side S 1 , the side S 2 , and the side S 4 . Thus, the source  26  is adjacent to the three sides S 1 , S 2 , and S 4 , and the drain  25  is adjacent to the side S 3  that is opposed to the side S 1  and not opposed to the sides S 2  and S 4 . As described above, in this modification, the amplifying transistor M 3  has nodes of the source  26  adjacent to three sides of one gate  23 . Also in this modification, the same effect as the configuration illustrated in  FIG.  4    can be obtained. As described above, in the amplifying transistor M 3  of the present embodiment, one source  26  may be adjacent to three or more sides of the gate  23 . 
       FIG.  9    is a schematic plan view of an amplifying transistor M 3  according to another modification of the present embodiment. The amplifying transistor M 3  has one gate  23 , one drain  25 , and one source  26 . As illustrated in  FIG.  9   , the gate  23  is a hexagon having six sides S 1 , S 2 , S 3 , S 4 , S 5 , and S 6 . The drain  25  is adjacent to the side S 3 . The source  26  is adjacent to the sides S 1 , S 2 , S 4 , S 5 , and S 6 . Thus, the source  26  is adjacent to the five sides S 1 , S 2 , S 4 , S 5 , and S 6 , and the drain  25  is adjacent to the side S 3  that is opposed to the side S 1  and not opposed to the sides S 2 , S 4 , S 5 , and S 6 . As described above, in this modification, the amplifying transistor M 3  has a node of the source  26  adjacent to one gate  23  on five sides. Also in this modification, the same effect as the configuration illustrated in  FIG.  4    can be obtained. As described above, the amplifying transistor M 3  of the present embodiment may have a polygonal shape having more than four sides, and one source  26  may be adjacent to more than four sides of the gate  23 . 
       FIG.  10    is a schematic plan view of an amplifying transistor M 3  according to another modification of the present embodiment. The amplifying transistor M 3  has one gate  23 , one drain  25 , and one source  26 . As illustrated in  FIG.  10   , the gate  23  is a hexagon having six sides S 1 , S 2 , S 3 , S 4 , S 5 , and S 6 . The drain  25  is adjacent to the side S 3 . The source  26  is adjacent to the side S 1 , the side S 5 , and the side S 6 . Thus, the source  26  is adjacent to the three sides S 1 , S 5 , and S 6 , and the drain  25  is adjacent to the side S 3  that is opposed to the side S 1  and not opposed to the sides S 2  and S 4 . As described above, in this modification, the amplifying transistor M 3  has nodes of the source  26  adjacent to three sides of one gate  23 . Also in this modification, the same effect as the configuration illustrated in  FIG.  4    can be obtained. As described above, the amplifying transistor M 3  of the present embodiment may have a polygonal shape having more than four sides, and one source  26  may be adjacent to less than four sides of the gate  23 . 
     Second Embodiment 
     The photoelectric conversion device according to the present embodiment will be described. Components similar to those in the first embodiment are denoted by the same reference numerals, and descriptions of these components may be omitted or simplified. 
       FIG.  11    is an equivalent circuit diagram of the pixel  20  according to the present embodiment. As illustrated in  FIG.  11   , the pixel  20  includes photoelectric conversion units PDA, PDB, PDC, and PDD, transfer transistors M 1 A, M 1 B, M 1 C, and M 1 D, a reset transistor M 2 , an amplifying transistor M 3 , and a selection transistor M 4 . The anodes of the photoelectric conversion units PDA, PDB, PDC, and PDD are connected to a ground node. The cathodes of the photoelectric conversion units PDA, PDB, PDC, and PDD are connected to the sources of the transfer transistors M 1 A, M 1 B, M 1 C, and M 1 D, respectively. The drains of the transfer transistors M 1 A, M 1 B, M 1 C, and M 1 D are connected to the floating diffusion portion FD. Control signals pTXA, pTXB, pTXC, and pTXD are supplied from the vertical scanning circuit  101  to gates of the transfer transistors M 1 A, M 1 B, M 1 C, and M 1 D, respectively. 
     In the present embodiment, charges can be transferred from the four transfer transistors M 1 A, M 1 B, M 1 C, and M 1 D to one floating diffusion FD. Thus, the reset transistor M 2 , the amplifying transistor M 3 , and the selection transistor M 4  are shared by the four photoelectric conversion units PDA, PDB, PDC, and PDD. 
       FIG.  12    is a schematic plan view of the pixel  20  according to the present embodiment.  FIG.  12    illustrates an arrangement of the photoelectric conversion units PDA, PDB, PDC, and PDD, the floating diffusion portion FD, and the gate, source, and drain of each transistor in a plan view with respect to the substrate. The gate  21 A,  21 B,  21 C, and  21 D illustrated in  FIG.  12    indicate an arrangement of the gate electrodes of the transfer transistors M 1 A, M 1 B, M 1 C, and M 1 D, respectively. The gates  22 ,  23 , and  24  illustrated in  FIG.  12    indicate an arrangement of the gate electrodes of the reset transistor M 2 , the amplifying transistor M 3 , and the selection transistor M 4 , respectively. 
     As illustrated in  FIG.  12   , the four photoelectric conversion units PDA, PDB, PDC, and PDD are arranged in two rows and two columns. The floating diffusion portion FD is arranged near the center of the four photoelectric conversion units PDA, PDB, PDC, and PDD. The gates  21 A,  21 B,  21 C, and  21 D are arranged between the photoelectric conversion units PDA, PDB, PDC, and PDD and the floating diffusion portion FD, respectively. The arrangement of the reset transistor M 2 , the amplifying transistor M 3 , and the selection transistor M 4  is the same as in  FIG.  3   . 
     Any of the configurations of  FIGS.  4  to  10    can be applied to the arrangement of the gate, source, and drain of the amplifying transistor M 3 . That is, as in the first embodiment, the amplifying transistor M 3  is configured such that the source thereof is adjacent to a plurality of sides of the gate  23 . Therefore, also in the present embodiment, it is possible to provide a photoelectric conversion device with improved performance as in the first embodiment. 
     In the present embodiment, the four photoelectric conversion units arranged to form two rows and two columns share one floating diffusion portion FD, but it is not limited thereto. The number, arrangement, and the like of the photoelectric conversion units can be appropriately changed. 
     In the configuration illustrated in  FIGS.  11  and  12   , a plurality of photoelectric conversion units sharing one floating diffusion portion FD may be arranged to correspond to one microlens. In this configuration, light transmitted through one microlens is incident on the plurality of photoelectric conversion units. By using signals accumulated in the plurality of photoelectric conversion units, focus detection of a phase difference detection method can be performed. The signal processing for focus detection can be performed by a signal processing unit or the like in a photoelectric conversion system including the photoelectric conversion device. 
     Third Embodiment 
     The photoelectric conversion device of the above embodiments can be applied to various equipment. Examples of the equipment include a digital still camera, a digital camcorder, a camera head, a copying machine, a facsimile, a mobile phone, a vehicle-mounted camera, an observation satellite, and a surveillance camera.  FIG.  13    is a block diagram of a digital still camera as an example of equipment. 
     The equipment  70  illustrated in  FIG.  13    includes a barrier  706 , a lens  702 , an aperture  704 , and an imaging device  700  (an example of a photoelectric conversion device). The equipment  70  further includes a signal processing unit (processing device)  708 , a timing generation unit  720 , a general control/operation unit  718  (control device), a memory unit  710  (storage device), a storage medium control I/F unit  716 , a storage medium  714 , and an external I/F unit  712 . At least one of the barrier  706 , the lens  702 , and the aperture  704  is an optical device corresponding to the equipment. The barrier  706  protects the lens  702 , and the lens  702  forms an optical image of an object on the imaging device  700 . The aperture  704  varies the amount of light passing through the lens  702 . The imaging device  700  is configured as in the above embodiments, and converts an optical image formed by the lens  702  into image data (image signal). The signal processing unit  708  performs various corrections, data compression, and the like on the captured image data output from the imaging device  700 . The timing generation unit  720  outputs various timing signals to the imaging device  700  and the signal processing unit  708 . The general control/operation unit  718  controls the entire digital still camera, and the memory unit  710  temporarily stores image data. The storage medium control I/F unit  716  is an interface for storing or reading image data on the storage medium  714 , and the storage medium  714  is a detachable storage medium such as a semiconductor memory for storing or reading captured image data. An external I/F unit  712  is an interface for communicating with an external computer or the like. The timing signal or the like may be input from the outside of the equipment. The equipment  70  may further include a display device (a monitor, an electronic view finder, or the like) for displaying information obtained by the photoelectric conversion device. The equipment includes at least a photoelectric conversion device. Further, the equipment  70  includes at least one of an optical device, a control device, a processing device, a display device, a storage device, and a mechanical device that operates based on information obtained by the photoelectric conversion device. The mechanical device is a movable portion (for example, a robot arm) that receives a signal from the photoelectric conversion device and operates. 
     Each pixel may include a plurality of photoelectric conversion units (a first photoelectric conversion unit and a second photoelectric conversion unit). The signal processing unit  708  may be configured to process a pixel signal based on the charges generated in the first photoelectric conversion unit and a pixel signal based on the charges generated in the second photoelectric conversion unit, and acquire distance information from the imaging device  700  to the object. 
     Fourth Embodiment 
       FIGS.  14 A and  14 B  are block diagrams of equipment relating to the vehicle-mounted camera according to the present embodiment. The equipment  80  includes the imaging device  800  (an example of a photoelectric conversion device) of the above-described embodiments and a signal processing device (processing device) that processes a signal from the imaging device  800 . The equipment  80  includes an image processing unit  801  that performs image processing on a plurality of pieces of image data acquired by the imaging device  800 , and a parallax calculation unit  802  that calculates parallax (phase difference of parallax images) from the plurality of pieces of image data acquired by the equipment  80 . The equipment  80  includes a distance measurement unit  803  that calculates a distance to an object based on the calculated parallax, and a collision determination unit  804  that determines whether or not there is a possibility of collision based on the calculated distance. Here, the parallax calculation unit  802  and the distance measurement unit  803  are examples of a distance information acquisition unit that acquires distance information to the object. That is, the distance information is information on a parallax, a defocus amount, a distance to the object, and the like. The collision determination unit  804  may determine the possibility of collision using any of these pieces of distance information. The distance information acquisition unit may be realized by dedicatedly designed hardware or a software module. Further, it may be realized by a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a combination thereof. 
     The equipment  80  is connected to a vehicle information acquisition device  810 , and can obtain vehicle information such as a vehicle speed, a yaw rate, and a steering angle. Further, the equipment  80  is connected to a control ECU  820  which is a control device that outputs a control signal for generating a braking force to the vehicle based on a determination result of the collision determination unit  804 . The equipment  80  is also connected to an alert device  830  that issues an alert to the driver based on the determination result of the collision determination unit  804 . For example, when the collision possibility is high as the determination result of the collision determination unit  804 , the control ECU  820  performs vehicle control to avoid collision or reduce damage by braking, returning an accelerator, suppressing engine output, or the like. The alert device  830  alerts the user by sounding an alarm such as a sound, displaying alert information on a screen of a car navigation system or the like, or providing vibration to a seat belt or a steering wheel. The equipment  80  functions as a control unit for controlling the operation of controlling the vehicle as described above. 
     In the present embodiment, an image of the periphery of the vehicle, for example, the front or the rear of the vehicle is captured by the equipment  80 .  FIG.  14 B  illustrates equipment in a case where an image is captured in front of the vehicle (image capturing range  850 ). The vehicle information acquisition device  810  as the image capturing control unit sends an instruction to the equipment  80  or the imaging device  800  to perform an image capturing operation. With such a configuration, the accuracy of distance measurement can be further improved. 
     Although the example of control for avoiding a collision to another vehicle has been described above, the embodiment is applicable to automatic driving control for following another vehicle, automatic driving control for not going out of a traffic lane, or the like. Furthermore, the equipment is not limited to a vehicle such as an automobile and can be applied to a movable body (movable apparatus) such as a ship, an airplane, a satellite, an industrial robot and a consumer use robot, or the like, for example. In addition, the equipment can be widely applied to equipment which utilizes object recognition or biometric authentication, such as an intelligent transportation system (ITS), a surveillance system, or the like without being limited to movable bodies. 
     Fifth Embodiment 
     The structure of the amplifying transistor M 3  described in the first embodiment and the second embodiment can be applied to devices other than the imaging device. In this embodiment, an example in which a transistor having a structure similar to that of the amplifying transistor M 3  is applied to a light emitting device will be described. Components similar to those in the first embodiment are denoted by the same reference numerals, and descriptions of these components may be omitted or simplified. 
     The light emitting device of the present embodiment can be used for an image display device, a display unit of an electronic device, a lighting device, and the like. Examples of the display device include a television receiver and a PC monitor. Examples of the electronic device include a smartphone, a mobile phone, and a camera. When the electronic device is a camera, the light emitting device of the present embodiment may be applied to a display unit such as an electronic view finder of the camera. 
       FIG.  15    is an equivalent circuit diagram of the pixel  50  of the light emitting device according to the present embodiment. The pixel  50  of the present embodiment is one unit of a light emitting unit in the light emitting device. In the display device, the number of pixels  50  may be one, or the pixels  50  may be arranged in one column or arranged in a plurality of rows and a plurality of columns. 
     The pixel  50  includes a selection transistor M 5 , a driving transistor M 6 , and a light emitting element LD. Each transistor is assumed to be a P-type MOS transistor, but may be an N-type MOS transistor. 
     The light emitting element LD is, for example, a light emitting diode such as an organic light emitting diode. The cathode of the light emitting element LD is connected to a ground node, and the anode of the light emitting element LD is connected to the drain of the driving transistor M 6 . The source of the driving transistor M 6  is connected to a power supply voltage node to which the voltage VDD is supplied. The gate of the driving transistor M 6  is connected to the drain of the selection transistor M 5 . The source of the selection transistor M 5  is connected to a signal line  51 . The signal line  51  is connected to a signal output circuit (not illustrated). 
     The signal output circuit supplies a voltage corresponding to a luminance of the light emitting element LD to the signal line  51 . A control signal pSC is input from a scanning circuit (not illustrated) to the gate of the selection transistor M 5 . When the selection transistor M 5  is turned on in response to the control signal pSC, a voltage corresponding to the voltage of the signal line  51  is applied to the gate of the driving transistor M 6 . Thus, a current flows through the driving transistor M 6 , and the voltage is charged in the capacitance between the anode and the cathode of the light emitting element LD, whereby the light emitting element LD emits light at a luminance corresponding to the voltage of the signal line  51 . 
     Here, any of the configurations of  FIGS.  4  to  10    can be applied to the arrangement of the gate, source, and drain of the driving transistor M 6 . That is, similar to the amplifying transistor M 3  of the first embodiment, the driving transistor M 6  is configured such that a plurality of sources is adjacent to a plurality of sides of the gate  23 . Thus, the transconductance gm can be increased, and a light emitting device with improved performance can be provided. 
     Since a state equivalent to a state in which the gate width W of the drain of the driving transistor M 6  is narrowed is realized, the drain current when the driving transistor M 6  is in an off state can be reduced, and an effect of improving a contrast ratio of an on state to an off state of the light emitting device can be obtained. 
     Modified Embodiments 
     The present invention is not limited to the above embodiments, and various modifications are possible. For example, an example in which some of the configurations of any of the embodiments are added to other embodiments or an example in which some of the configurations of any of the embodiments are replaced with some of the configurations of other embodiments is also an embodiment of the present invention. 
     The disclosure of this specification includes a complementary set of the concepts described in this specification. That is, for example, if a description of “A is B” (A = B) is provided in this specification, this specification is intended to disclose or suggest that “A is not B” even if a description of “A is not B” (A ≠ B) is omitted. This is because it is assumed that “A is not B” is considered when “A is B” is described. 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-184890, filed Nov. 12, 2021, which is hereby incorporated by reference herein in its entirety.