Solid-state imaging element and video recording apparatus

1. A solid-state imaging element comprising:

a first semiconductor substrate that includes a floating diffusion that temporarily holds an electric signal output from a photoelectric conversion element; and

a second semiconductor substrate that faces the first semiconductor substrate, wherein

the second semiconductor substrate includes:

a first transistor disposed on a side facing the first semiconductor substrate, the first transistor including:

a channel extending along a thickness direction of the second semiconductor substrate; and

a multi-gate extending along the thickness direction of the second semiconductor substrate and sandwiching the channel, wherein the multi-gate of the first transistor is connected to the floating diffusion;

a source region that extends from one surface side of the second semiconductor substrate and reaches another surface side of the second semiconductor substrate,

wherein the one surface side of the second semiconductor substrate is opposite the another surface side of the second semiconductor substrate, and

wherein the another surface side of the second semiconductor substrate faces the first semiconductor substrate; and

a drain region that extends from the one surface side of the second semiconductor substrate and reaches the another surface side of the second semiconductor substrate,

wherein the source region is connected to a signal line that transmits the electric signal from the one surface side of the second semiconductor substrate, and

wherein the drain region is connected to a power supply potential from the one surface side of the second semiconductor substrate.

2. The solid-state imaging element according to claim 1 , further comprising:

a contact that connects a surface of the multi-gate and a surface of the floating diffusion, the surface of the multi-gate facing the surface of the floating diffusion.

3. The solid-state imaging element according to claim 1 , wherein

the second semiconductor substrate includes a second transistor disposed on a side facing the first semiconductor substrate, the second transistor including a source region, and

the multi-gate of the first transistor is connected to the source region of the second transistor.

4. A solid-state imaging element, comprising:

a first semiconductor substrate that includes a floating diffusion that temporarily holds an electric signal output from a photoelectric conversion element; and

a second semiconductor substrate that faces the first semiconductor substrate, wherein

the second semiconductor substrate includes:

a first transistor disposed on a side facing the first semiconductor substrate, the first transistor including:

a channel extending along a thickness direction of the second semiconductor substrate; and

a multi-gate extending along the thickness direction of the second semiconductor substrate and sandwiching the channel, wherein the multi-gate of the first transistor is connected to the floating diffusion, and wherein the first transistor is an amplification transistor that amplifies the electric signal that is output from the photoelectric conversion element;

a second transistor disposed on a side facing the first semiconductor substrate, the second transistor including:

a channel extending along a thickness direction of the second semiconductor substrate; and

a multi-gate extending along the thickness direction of the second semiconductor substrate and sandwiching the channel,

wherein the multi-gate of the second transistor is connected to a signal line that transmits the electric signal from one surface side of the second semiconductor substrate, the one surface side being opposite to another surface side of the second semiconductor substrate facing the first semiconductor substrate, and wherein the second transistor is a reset transistor that resets a potential of the multi-gate of the amplification transistor to a power supply potential; and

a third semiconductor substrate disposed on a side of the second semiconductor substrate opposite to the first semiconductor substrate, the third semiconductor substrate facing the second semiconductor substrate, wherein

the third semiconductor substrate includes a selection transistor that selects whether or not to transmit the electric signal amplified in the amplification transistor to the signal line.

5. The solid-state imaging element according to claim 4 , wherein

the first semiconductor substrate includes a transfer transistor that transfers the electric signal to the amplification transistor, the electric signal being output from the photoelectric conversion element.

6. A video recording apparatus, comprising:

a solid-state imaging element;

an optical system that takes incident light from a subject to form an image on an imaging area of the solid-state imaging element; and

a signal processing circuit that performs processing on an output signal from the solid-state imaging element, wherein

the solid-state imaging element includes:

a first semiconductor substrate that includes a floating diffusion that temporarily holds an electric signal output from a photoelectric conversion element; and

a second semiconductor substrate that faces the first semiconductor substrate,

wherein the second semiconductor substrate includes a first transistor disposed on a side facing the first semiconductor substrate, the first transistor including:

a channel extending along a thickness direction of the second semiconductor substrate; and

a multi-gate extending along the thickness direction of the second semiconductor substrate and sandwiching the channel, wherein the multi-gate of the first transistor is connected to the floating diffusion;

a source region that extends from one surface side of the second semiconductor substrate and reaches another surface side of the second semiconductor substrate,

wherein the one surface side of the second semiconductor substrate is opposite the another surface side of the second semiconductor substrate, and

wherein the another surface side of the second semiconductor substrate faces the first semiconductor substrate; and

a drain region that extends from the one surface side of the second semiconductor substrate and reaches the another surface side of the second semiconductor substrate,

wherein the source region is connected to a signal line that transmits the electric signal from the one surface side of the second semiconductor substrate, and

wherein the drain region is connected to a power supply potential from the one surface side of the second semiconductor substrate.