Patent ID: 7582522

Claim:
A method for making an image sensor, the method comprising: forming a first well and a second well in a substrate, the first well and the second well being different; forming a gate oxide layer on the substrate; depositing a first gate region and a second gate region on the gate oxide layer, the first gate region being associated with the first well, the second gate region being associated with the second well; forming a third well in the substrate, the third well being associated with a photodiode; implanting a first plurality of ions to form a first lightly doped source region and a first lightly doped drain region in the first well; implanting a second plurality of ions to form at least a second lightly doped drain region in the second well; and implanting a third plurality of ions to form a source in the second well with a first implant dose ranging from 10 3 cm −2 to 10 5 cm −2 , wherein the third plurality of ions are implanted before forming any spacers.