CMOS image sensors and related methods of fabricating CMOS image sensors are disclosed. Fabrication of a CMOS image sensor can include forming a first impurity region having a first conductivity type in a semiconductor substrate. A second impurity region having a second conductivity type is formed in the semiconductor substrate adjacent to the first impurity region. A third impurity region having the first conductivity type is formed in the semiconductor substrate and located below the second impurity region. A transfer gate is formed on the semiconductor substrate and at least partially overlaps the first, second, and third impurity regions. A photo sensitive device is formed in the semiconductor substrate and adjacent to one side of the transfer gate. A floating diffusion region is formed in the semiconductor substrate and located adjacent to an opposite side of the transfer gate from the photosensitive device.