Image sensor

An image sensor comprising:

• a first element isolation region in a substrate, the first element isolation region defining a unit pixel and having a first conductivity type;
• a first photoelectric conversion region in the unit pixel, the first photoelectric conversion region having a second conductivity type different from the first conductivity type;
• a second photoelectric conversion region in the unit pixel, the second photoelectric conversion region having the second conductivity type;
• a second element isolation region having the first conductivity type, the second element isolation region in the substrate, the second element isolation region between the first photoelectric conversion region and the second photoelectric conversion region;
• a third element isolation region having the first conductivity type, the third element isolation region in the substrate, the third element isolation region between the first element isolation region and the second element isolation region;
• a floating diffusion region in the substrate, the floating diffusion region having the second conductivity type;
• a first channel region in the substrate between the first photoelectric conversion region and the floating diffusion region, the first channel region having the first conductivity type with a first impurity concentration;
• a second channel region in the substrate between the second photoelectric conversion region and the floating diffusion region, the second channel region having the first conductivity type with a second impurity concentration lower than the first impurity concentration;
• a first transfer gate on the first channel region, at least a part of the first transfer gate buried in the substrate;
• and
• a second transfer gate on the second channel region,
• wherein a third impurity concentration of the third element isolation region is less than the first impurity concentration and less than the second impurity concentration.

An image sensor comprising:

• a first element isolation region in a substrate, the first element isolation region defining a unit pixel and having a first conductivity type;
• a first photoelectric conversion circuitry in the unit pixel;
• a second photoelectric conversion circuitry in the unit pixel;
• a second element isolation region in the substrate between the first photoelectric conversion circuitry and the second photoelectric conversion circuitry, the second element isolation region having the first conductivity type;
• a third element isolation region in the substrate between the first element isolation region and the second element isolation region, the third element isolation region having the first conductivity type with an impurity concentration lower than those of both the first and the second element isolation regions;
• a first transfer gate adjacent to the first photoelectric conversion circuitry, the first transfer gate forming a first channel region in the substrate;
• and
• a second transfer gate adjacent to the second photoelectric conversion circuitry, the second transfer gate forming a second channel region in the substrate,
• wherein in response to the first transfer gate being in an off state, a potential of the first channel region is at a first off potential,
• in response to the second transfer gate being in an off state, a potential of the second channel region is at a second off potential different from the first off potential, and
• a potential of the third element isolation region is less than the first off potential and less than the second off potential.