Imaging device, manufacturing method thereof, and electronic device

A manufacturing method of an imaging device comprising a single crystal silicon substrate and a support substrate,

• wherein a photoelectric-conversion device is formed by providing a region whose conductivity type is opposite to a conductivity type of the single crystal silicon substrate on a first surface side of the single crystal silicon substrate,
• wherein a first insulating layer and a first conductive layer which is electrically connected to the photoelectric-conversion device are formed over the photoelectric-conversion device,
• wherein a transistor which comprises a metal oxide in its channel formation region is formed over the support substrate,
• wherein a second insulating layer and a second conductive layer which is electrically connected to the transistor are formed over the transistor,
• wherein a surface of the first insulating layer and a surface of the second insulating layer are bonded and a surface of the first conductive layer and a surface of the second conductive layer are bonded, and
• wherein a surface opposite to the first surface of the single crystal silicon substrate is grinded and polished to make a light-absorption layer of the photoelectric-conversion device thin.

An imaging device comprising a first layer, a second layer, a third layer, and a fourth layer stacked in this order,

• wherein the first layer, the second layer, the third layer, and the fourth layer comprise a region where the first layer, the second layer, the third layer, and the fourth layer overlap with each other,
• wherein the first layer comprises an optical-filter layer,
• wherein the second layer comprises single crystal silicon,
• wherein the third layer comprises a device-formation layer,
• wherein the fourth layer comprises a support substrate,
• wherein the second layer comprises a photoelectric-conversion device whose light-absorption layer is the single crystal silicon,
• wherein the third layer comprises a transistor which comprises a metal oxide in its channel formation region,
• wherein the photoelectric-conversion device and the transistor are electrically connected, and
• wherein the photoelectric-conversion device receives light having passed through the optical-filter layer.