Abstract: A CMOS image sensor 101 comprises an active layer 11 of a first conductivity type arranged to be reversed biased and a pixel 20 comprising a photosensitive element comprising a well 22 of a second conductivity type and a well 21 of the first conductivity type containing active CMOS elements for reading and resetting the photosensitive element. The CMOS image sensor further comprises a doped buried layer 111 of the second conductivity type in the active layer beneath the well of the first conductivity type. The buried layer is arranged to extend a depletion region below the well of the second conductivity type also below the well of the first conductivity type.