Image sensor including junctionless transfer transistor

Abstract

An image sensor includes a substrate, a polysilicon-vertical gate, a photoelectric conversion element, a channel, and a floating diffusion region. The substrate has a front surface and a back surface that opposes the front surface. The polysilicon-vertical gate is disposed in an upper region adjacent to the front surface of the substrate and extends into the substrate. The photoelectric conversion element is disposed at a lower position within the substrate with respect to the polysilicon-vertical gate. The channel is disposed adjacent to the polysilicon-vertical gate and doped with dopants of a same conductivity type as the photoelectric conversion element. The floating diffusion region is disposed in the upper region of the substrate and adjacent to the polysilicon-vertical gate in a first parallel direction that is parallel to the front surface of the substrate. The polysilicon-vertical gate, the photoelectric conversion element, and the floating diffusion region constitute a junctionless transfer transistor.