there is no need to couple the photogate 230 and the transfer gate 236 with a doped region between the gates to enable charge transfer this more compact structure results in increased charge transfer efficiency of the accumulated charges generated by photogate 230 to the floating diffusion node 246 however there are significant processing difficulties in the fabrication methods used to create this semiconductor structure the oxidation of the photogate stack 230 prior to transfer gate stack 236 formation results in asperities points and other defects in the oxide layer insulating the transfer gate from the photogate resulting in low breakdown of the insulating gate oxide between these two overlying gate structures improper electrical functioning and poor processing yield additionally the oxidation of the first polysilicon layer or other suitable conductive layer prior to the deposition of the second polysilicon or other suitable conductive material layer which will form the transfer gate 236 forms the second gate oxide under the transfer gate as device configurations have shrunk to improve performance and yield the gate oxide must be grown thinner to maintain low threshold voltages and maintain performance in the more compact configurations the thinning of the second gate oxide continues to cause degradation.