Patent ID: 7759706

Claim:
A solid-state imaging device including an array of unit pixels, each unit pixel comprising: a photoelectric conversion element; and an amplifier transistor for amplifying a signal corresponding to charge obtained by photoelectric conversion through the photoelectric conversion element, wherein the amplifier transistor is a buried channel MOS transistor comprised of three terminals including a source, drain, and gate terminal, the buried channel extending under the gate terminal and from the source terminal to the drain terminal, wherein at least two different first conductivity type impurities having different diffusion coefficients are implanted into the buried channel region of the amplifier transistor, and the impurities are distributed such that a density of the implanted impurity with the lower diffusion coefficient is higher than the density of the implanted impurity with the higher diffusion coefficient in a region of the buried channel closest to the gate insulating film of the amplifier transistor, and further wherein a gate-source voltage is less than 1.5 volts and the amplifier transistor is a MOS transistor comprising a channel of a first conductivity type, the gate electrode of the transistor comprises polysilicon of a second conductivity type different than the first conductivity type.