Image sensors

An image sensor comprising:

• a substrate;
• a first region formed in the substrate;
• a first photoelectric conversion element (PD) on the first region;
• a first microlens covering the first PD;
• a floating diffusion region (FD) electrically coupled to the first PD;
• a first transfer transistor electrically coupled between the first PD and the FD;
• and
• first to fifth pixel transistors, each electrically coupled to the FD,
• wherein the first and second pixel transistors are selected from the group consisting of a reset transistor, a selection transistor, and a driving transistor,
• wherein none of the first to fifth pixel transistors is a transfer transistor, and
• wherein the first and second pixel transistors vertically overlap the first region.

An image sensor comprising:

• a substrate;
• a first region formed in the substrate;
• a first photoelectric conversion element (PD) on the first region;
• a first microlens covering the first PD;
• a floating diffusion region (FD) electrically coupled to the first PD;
• a first transfer transistor electrically coupled between the first PD and the FD;
• and
• first to fifth pixel transistors, each electrically coupled to the FD,
• wherein the first to third pixel transistors are each selected from the group consisting of a reset transistor, a selection transistor, and a driving transistor,
• wherein none of the first to fifth pixel transistors is a transfer transistor,
• wherein the first and second pixel transistors vertically overlap the first region, and
• wherein the first to fifth pixel transistors are aligned linearly along a first direction parallel to a surface of the substrate.