Solid state image pickup device and camera
An object of the present invention is to simultaneously realize the enlargement of a dynamic range and the downsizing of a pixel. An additional capacitor CS is composed by using: a first capacitor formed of a first diffusion layer, a second diffusion layer and a P well by layering the P well, the first diffusion layer, a first dielectric film, a first polysilicon layer, a second dielectric film and a second polysilicon layer; a second capacitor formed of the second diffusion layer, the first polysilicon layer and the first dielectric film; and a third capacitor formed of the first polysilicon layers, a second polysilicon layer, and a second dielectric film. Thereby, the additional capacitor CS for accumulating carriers overflown from a photodiode PD can secure a required capacitance value while making its size as small as possible.
1. A solid state image pickup device including a plurality of pixels, the device comprising:
a photoelectric conversion region for accumulating carriers generated by incident light;
a first transfer switch for transferring the carriers accumulated in the photoelectric conversion region;
a floating diffusion region for making the carriers accumulated in the photoelectric conversion region flow therein through the first transfer switch;
a carrier accumulating region for accumulating at least a part of carriers overflowed from the photoelectric conversion region; and
a second transfer switch for transferring the carriers accumulated in the carrier accumulating region to the floating diffusion region;
wherein the carrier accumulating region includes:
one part of a semiconductor region of a first conductivity type,
a first dielectric film formed on the one part of the semiconductor region,
a first electrode layer formed on the first dielectric film,
a second dielectric film formed on the first electrode layer,
a second electrode layer formed on the second dielectric film,
a first impurity-diffused layer which is formed in the semiconductor region so as to be vertically adjacent to the first dielectric film and contains impurities of a second conductivity type opposite to the first conductivity type, and
a second impurity-diffused layer which is formed in the semiconductor region so as to be horizontally adjacent to the first impurity-diffused layer, and contains the impurities of the second conductivity type.
2. The solid state image pickup device according to claim 1 , wherein
the first electrode layer is connected to a power supply potential or a ground potential, and
the second impurity-diffused layer, the second electrode layer and the second transfer switch are interconnected.
3. The solid state image pickup device according to claim 1 , wherein
the second electrode layer is connected to a power supply potential or a ground potential,
the first electrode layer and the second transfer switch are interconnected, and
the second impurity-diffused layer is connected to the ground potential.
4. The solid state image pickup device according to claim 2 , wherein the second transfer switch includes:
one part of the semiconductor region, an insulation film formed on the surface of the semiconductor region,
the second impurity-diffused layer,
a third impurity-diffused layer which is formed at a position facing the second impurity-diffused layer through a lower region of the insulation film and contains the impurities of the second conductivity type, and
an electrode layer formed on the insulation film.