Method of making integrated CMOS and CTD by selective implantation

摘要

A method of forming combination CMOS field effect transistors optionally with a charge transfer device in a single substrate. Different resistivities in the P type wells of the substrate are formed by a combination of masks; a high energy low dosage ion implantation of impurity passes through one mask but not the other, and a low energy high dosage ion implantation of the impurity is stopped by both masks. A significant number of fabrication steps is thus saved, and the devices so fabricated are threshold and field voltage compatible.