There is provided a semiconductor apparatus including a first semiconductor region of a first conductive type in which a potential to be detected appears, a second semiconductor region of a second conductive type forming a p-n junction with the first semiconductor region, an amplification transistor including a gate to which the first semiconductor region is connected, and a reset transistor configured to reset a potential of the first semiconductor region. In the semiconductor apparatus, one of a source and a drain of the reset transistor is connected to the first semiconductor region, and the other one of the source and the drain of the reset transistor is connected to the second semiconductor region.