Each unit pixel includes a photoelectric converter, an n-type impurity region forming an accumulation diode together with the semiconductor region, the accumulation diode accumulating a signal charge generated by the photoelectric converter, an amplifier transistor including a gate electrode electrically connected to the impurity region, and an isolation region formed around the amplifier transistor and implanted with p-type impurities. The amplifier transistor includes an n-type source/drain region formed between the gate electrode and the isolation region, and a channel region formed under the gate electrode. A gap in the isolation region is, in a gate width direction, wider at a portion including the channel region than at a portion including the source/drain region.