To provide a semiconductor device and an imaging apparatus capable of improving performance of a transistor. The semiconductor device includes a semiconductor substrate and a transistor provided on the semiconductor substrate. A gate electrode of the transistor includes a first part disposed at a position opposing the semiconductor substrate via a gate insulating film of the transistor and configured to form a channel on the semiconductor substrate and a second part positioned on top of the first part and configured to have a smaller contribution toward the formation of the channel than the first part. The first part includes a gate end which is positioned on a side of one region of a drain region and a source region of the transistor and in which an electric field concentrates with respect to the one region. The gate end is positioned above or below a surface of the one region via a stepped portion provided on a side of a first surface of the semiconductor substrate and is flush with a side surface of the second part.

An image sensor device includes nanostructures for improving light absorption efficiency. The image sensor device includes a substrate, a light absorption region, and a nanostructure array. The light absorption region is over the substrate. The nanostructure array us over the light absorption region. The nanostructure array includes a plurality of nanostructures repeatedly arranged from a top view.

An image sensor device includes nanostructures for improving light absorption efficiency. The image sensor device includes a substrate doped with a first dopant of a first conductivity type, and a light absorption region over the substrate. The light absorption region is doped with a second dopant of a second conductivity type. The second conductivity type is different from the first conductivity type. The nanostructures overlap the light absorption region. One of the nanostructures has a bottom surface at a different level than a top surface of the light absorption region.