Imaging device by buried photodiode structure

An image sensor having a plurality of unit pixels arranged one-dimensionally or two-dimensionally, each of the unit pixels comprising:

• a buried photodiode comprising a charge storage region including a buried portion and a protruding portion connected to the buried portion, the protruding portion having an upper end lying higher than the buried portion;
• an insulator having a thick portion disposed above the buried portion, the thick portion configured to bury the protruding portion under the thick portion, and a thin portion disposed on the upper end of the protruding portion;
• a floating electrode selectively disposed on the thin portion of the insulator, capacitively coupled to the protruding portion of the charge storage region of the photodiode through the thin portion of the insulator, and configured to be driven into a floating state;
• a first transfer transistor connected to the charge storage region of the photodiode configured to extract and initialize carriers, which are generated by light and stored in the charge storage region;
• a second transfer transistor connected between the floating electrode and a power supply at an initialization potential, the power supply configured to apply the initialization potential to the floating electrode;
• and
• a buffer transistor having a gate electrode connected to the floating electrode, configured to read out a potential of the floating electrode.