Patent attributes
An image sensor includes a photodiode disposed in a first semiconductor material and a floating diffusion disposed proximate to the photodiode in the first semiconductor material. A source follower transistor is disposed in part in a second semiconductor material and includes: a first doped region, a third doped region, and a second doped region with an opposite polarity as the first doped region and the third doped region, and a gate electrode coupled to the floating diffusion and disposed in the first semiconductor material and aligned with the second doped region in the second semiconductor material of the source follower transistor.