An embodiment includes: a semiconductor substrate including a pixel well region and a peripheral well region; a pixel ground line arranged above the pixel well region; a pixel well contact between the pixel ground line and the pixel well region; pixels arranged to form columns in the pixel well region; a reference signal generation circuit arranged in the peripheral well region; and comparator units arranged in the peripheral well region, provided to respective columns, and each configured to receive the pixel signal from the pixels on a corresponding column and the reference signal. Each comparator unit includes a comparator having a first input node that receives the pixel signal and a second input node that receives the reference signal, a first capacitor unit between the reference signal generation circuit and the second input node, and a second capacitor unit between the second input node and the pixel ground line.