regions 120 as illustrated in fig4 as noted above with respect to fig2 any suitable doping process may be used such as ion implantation the photodiode region 115 is shown in p well 112 reference is now made to fig5 a second mask and resist not shown are applied to the photodiode 115 to form the first n type region 130 such that n type region 130 is spaced away from the field oxide regions 120 to facilitate reduction of the electric field across the p n photodiode junction at the photodiode edge any suitable doping process may be used to form n type region 130 such as ion implantation a second n type region 110 is formed within the boundaries of the first n type region 130 a third resist and mask not shown is applied to the photodiode 115 and the substrate is doped to form second n type region 110 as set forth above any suitable doping process may be used such as ion implantation again as was true of fig3 it is important that the second n type region 110 is doped to a higher dopant concentration than the first n type region 130 such that the charge collected in the photodiode 115 is isolated in the second n type region 110 the resist and mask are removed leaving a structure as illustrated in fig6 for the photodiode 115 of the first embodiment the processing is essentially complete at this stage and conventional processing methods may then be used to form contacts and wiring to connect the photodiode 115 to.