A highly sensitive imaging device that can perform imaging even under a low illuminance condition is provided. One electrode of a photoelectric conversion element is electrically connected to one of a source electrode and a drain electrode of a first transistor and one of a source electrode and a drain electrode of a third transistor. The other of the source electrode and the drain electrode of the first transistor is electrically connected to a gate electrode of the second transistor. The other electrode of the photoelectric conversion element is electrically connected to a first wiring. A gate electrode of the first transistor is electrically connected to a second wiring. When a potential supplied to the first wiring is HVDD, the highest value of a potential supplied to the second wiring is lower than HVDD.

A semiconductor device having a structure which can prevent a decrease in electrical characteristics due to miniaturization is provided. The semiconductor device includes, over an insulating surface, a stack in which a first oxide semiconductor layer and a second oxide semiconductor layer are sequentially formed, and a third oxide semiconductor layer covering part of a surface of the stack. The third oxide semiconductor layer includes a first layer in contact with the stack and a second layer over the first layer. The first layer includes a microcrystalline layer, and the second layer includes a crystalline layer in which c-axes are aligned in a direction perpendicular to a surface of the first layer.

A highly accurate imaging device or a highly accurate imaging device capable of detecting differences is provided. A configuration including a circuit in which variation in threshold voltage among amplifier transistors of pixels is corrected is employed. The configuration reduces variation in difference data due to variation in the threshold voltage among the amplifier transistors of the pixels to obtain highly accurate imaging data. Furthermore, charge corresponding to difference data between imaging data in an initial frame and imaging data in a current frame is accumulated in pixels and the difference data is read from each pixel, whereby highly accurate difference data is obtained when whether there is a difference between the initial frame and the current frame is determined.

A solid state imaging element according to the invention includes: a semiconductor layer of a first conductivity type; a gate insulation film on the semiconductor layer; a gate electrode on the gate insulation film; a first impurity region of a second conductivity type in the semiconductor layer and in a region outside the gate electrode on a first end portion side; a second impurity region of the second conductivity type in the semiconductor layer and in a region outside the gate electrode on a second end portion side that is opposite to the first end portion of the gate electrode; and a third impurity region of the first conductivity type over the second impurity region in the semiconductor layer at a position separate from the second end portion of the gate electrode as viewed in plan view, and is in contact with the second impurity region.

An image pickup device includes: a photodiode provided in a silicon substrate, and configured to generate electric charge corresponding to an amount of received light, by performing photoelectric conversion; and a transfer transistor provided at an epitaxial layer on the silicon substrate, and configured to transfer the electric charge generated in the photodiode, wherein the transfer transistor includes a gate electrode and a channel region, the gate electrode being embedded in the epitaxial layer, and the channel region surrounding the gate electrode, and the channel region has, in a thickness direction, a concentration gradient in which a curvature of a potential gradient is free from a mixture of plus and minus signs.

An imaging device which can perform imaging with a global shutter system and in which transistors are shared by pixels is provided. The imaging device includes first and second photoelectric conversion elements and first to sixth transistors. Active layers of the first to fourth transistors each include an oxide semiconductor. The imaging device has a configuration in which a reset transistor and an amplifier transistor are shared by a plurality of pixels and can perform imaging with a global shutter system. In addition, the imaging device can be used as a high-speed camera.

A change in electrical characteristics of a semiconductor device including an interlayer insulating film over a transistor including an oxide semiconductor as a semiconductor film is suppressed. The structure includes a first insulating film which includes a void portion in a step region formed by a source electrode and a drain electrode over the semiconductor film and contains silicon oxide as a component, and a second insulating film containing silicon nitride, which is provided in contact with the first insulating film to cover the void portion in the first insulating film. The structure can prevent the void portion generated in the first insulating film from expanding outward.

The present disclosure provides a detector substrate and a flat panel detector, the detector substrate includes a substrate base and detector pixel units on the substrate base, each detector pixel unit includes: a driver circuit; a photoelectric conversion device disposed on a side, away from the substrate base, of the driver circuit, the photoelectric conversion device including at least two photoelectric conversion structures connected in series, a bottom electrode of a first photoelectric conversion structure being electrically connected with the driver circuit, and a top electrode of an n.sup.th photoelectric conversion structure being electrically connected with a bottom electrode of an (n+1).sup.th photoelectric conversion structure, with n being greater than or equal to 1; and a bias voltage line on a side of the photoelectric conversion device away from the substrate base, the bias voltage line being electrically connected to a top electrode of a last photoelectric conversion structure.

An image sensing device includes a pixel array including a plurality of unit pixels consecutively arranged and structured to generate an electrical signal in response to incident light by performing photoelectric conversion of the incident light. The unit pixels are isolated from each other by first device isolation structures. Each of the unit pixels includes a photoelectric conversion element structured to generate photocharges by performing photoelectric conversion of the incident light, a floating diffusion region structured to receive the photocharges, a transfer transistor structured to transfer the photocharges generated by the photoelectric conversion element to the floating diffusion region, and a well tap region structured to apply a bias voltage to a well region. The well tap region is disposed at a center portion of a corresponding unit pixel.

An image sensor structure and methods of forming the same are provided. An image sensor structure according to the present disclosure includes a semiconductor substrate including a photodiode, a transfer gate transistor disposed over the semiconductor substrate and having a first channel area, a first dielectric layer disposed over the semiconductor substrate, a semiconductor layer disposed over the first dielectric layer, a source follower transistor disposed over the semiconductor layer and having a second channel area, a row select transistor disposed over the semiconductor layer and having a third channel area, and a reset transistor disposed over the semiconductor layer and having a fourth channel area. The second channel area is greater than the first channel area, the third channel area or the fourth channel area.