Image sensor including transistor including protruding channel electrode

An image sensor comprising:

• a photodiode formed in a substrate;
• and
• a transfer transistor structure, a source follower transistor structure, and a selection transistor structure each formed on the substrate,
• wherein the transfer transistor structure comprises a transfer transistor channel electrode and a transfer transistor gate structure that surrounds side surfaces of the transfer transistor channel electrode,
• wherein the source follower transistor structure comprises a source follower transistor channel electrode and a source follower transistor gate structure that surrounds side surfaces of the source follower transistor channel electrode,
• wherein the selection transistor structure comprises a selection transistor channel electrode and a selection transistor gate structure that surrounds side surfaces of the selection transistor channel electrode,
• wherein the transfer transistor channel electrode, the source follower transistor channel electrode, and the selection transistor channel electrode protrude from a surface of the substrate, and
• wherein the transfer transistor structure, the source follower transistor structure, and the selection transistor structure are vertically aligned with and overlap the photodiode.

An image sensor comprising:

• a lower device and an upper device stacked on the lower device,
• wherein the lower device comprises a logic circuit disposed on a lower substrate,
• wherein the upper device comprises a plurality of photodiodes formed in an upper substrate, a plurality of cell circuits disposed on a bottom surface of the upper substrate, and a plurality of color filters disposed on a top surface of the upper substrate,
• wherein each of the plurality of cell circuits comprises a transfer transistor structure, a source follower transistor structure, and a selection transistor structure,
• wherein the transfer transistor structure of each of the plurality of cell circuits is vertically aligned with one of the plurality of photodiodes, and comprises a transfer transistor channel electrode protruding from the bottom surface of the upper substrate and a transfer transistor gate structure surrounding side surfaces of the transfer transistor channel electrode,
• wherein the source follower transistor structure of each of the plurality of cell circuits is vertically aligned with one of the plurality of photodiodes, and comprises a source follower transistor channel electrode protruding from the bottom surface of the upper substrate and a source follower transistor gate structure surrounding side surfaces of the source follower transistor channel electrode, and
• wherein the selection transistor structure of each of the plurality of cell circuits is vertically aligned with one of the plurality of photodiodes, and comprises a selection transistor channel electrode protruding from the bottom surface of the upper substrate and a selection transistor gate structure surrounding side surfaces of the selection transistor channel electrode.