An imaging device comprising: a plurality of pixels, each including a photoelectric conversion unit , a floating diffusion configured to hold charge generated in the photoelectric conversion unit , an amplifier transistor electrically connected to the floating diffusion , and a capacitor including an electrode , the capacitor being disposed so that electrical connection of the capacitor to the floating diffusion is switchable in accordance with a signal supplied to the electrode , wherein the electrical connection of the capacitor to the floating diffusion is switched to vary a capacitance value of an input node of the amplifier transistor , wherein each of the plurality of pixels has an active region including a first region and a second region , the first region and the second region being arranged with the electrode therebetween in plan view, wherein a portion that is a portion of the active region and that is located under the electrode forms at least a portion of the capacitor , wherein the first region includes a first semiconductor region of a first conductivity type, the first semiconductor region forming at least a portion of the floating diffusion , wherein the second region includes a second semiconductor region of a second conductivity type opposite to the first conductivity type, wherein an insulating film is disposed on the second semiconductor region , and wherein the second semiconductor region forms an interface with an insulator isolation portion, characterized in that at least a part of the second region does not overlap the electrode and in that the insulator isolation portion is provided on the side of the second region opposite the electrode. a plurality of pixels, each including a photoelectric conversion unit , a floating diffusion configured to hold charge generated in the photoelectric conversion unit , an amplifier transistor electrically connected to the floating diffusion , and a capacitor including an electrode , the capacitor being disposed so that electrical connection of the capacitor to the floating diffusion is switchable in accordance with a signal supplied to the electrode , a photoelectric conversion unit , a floating diffusion configured to hold charge generated in the photoelectric conversion unit , an amplifier transistor electrically connected to the floating diffusion , and a capacitor including an electrode , the capacitor being disposed so that electrical connection of the capacitor to the floating diffusion is switchable in accordance with a signal supplied to the electrode , wherein the electrical connection of the capacitor to the floating diffusion is switched to vary a capacitance value of an input node of the amplifier transistor , wherein each of the plurality of pixels has an active region including a first region and a second region , the first region and the second region being arranged with the electrode therebetween in plan view, wherein a portion that is a portion of the active region and that is located under the electrode forms at least a portion of the capacitor , wherein the first region includes a first semiconductor region of a first conductivity type, the first semiconductor region forming at least a portion of the floating diffusion , wherein the second region includes a second semiconductor region of a second conductivity type opposite to the first conductivity type, wherein an insulating film is disposed on the second semiconductor region , and wherein the second semiconductor region forms an interface with an insulator isolation portion, characterized in that at least a part of the second region does not overlap the electrode and in that the insulator isolation portion is provided on the side of the second region opposite the electrode. <EOS>