Patent ID: 8154060

Claim:
An image sensor comprising: a first electrode for forming an electric field storing signal charges; a second electrode for forming another electric field increasing the number of the signal charges by impact ionization; a photoelectric conversion portion generating the signal charges; a third electrode provided to be adjacent to said photoelectric conversion portion for transferring the signal charges; a voltage conversion portion for converting the signal charges into a voltage; a fourth electrode provided to be adjacent to said voltage conversion portion for transferring the signal charges to said voltage conversion portion; a transfer channel provided under said first electrode, said second electrode, said third electrode and said fourth electrode for performing a signal charge transferring operation and a signal charge increasing operation; and a potential control portion controlling at least either the potential of a portion of said transfer channel corresponding to said third electrode or the potential of another portion of said transfer channel corresponding to said fourth electrode to be lower than the potentials of portions of said transfer channel corresponding to said first electrode and said second electrode respectively always in said signal charge increasing operation; wherein each of pixels includes said first electrode, said second electrode, said third electrode, said fourth electrode, said photoelectric conversion portion, said voltage conversion portion, and said transfer channel.