Each unit pixel includes a photoelectric converter formed above a semiconductor region, an amplifier transistor formed in the semiconductor region, and including a gate electrode connected to the photoelectric converter, a reset transistor configured to reset a potential of the gate electrode, and an isolation region formed in the semiconductor region between the amplifier transistor and the reset transistor to electrically isolate the amplifier transistor from the reset transistor. The amplifier transistor includes a source/drain region. The source/drain region has a single source/drain structure.