Patent ID: 7807555

Claim:
A method of forming field effect transistors in an integrated circuit which includes forming a dual structure body region of a first conductivity type in a first region of the substrate, forming a source region of a second conductivity type in the surface of the dual structure body region portions, and forming a drain contact region of the second conductivity type in the surface of a drain region in the substrate, the method of forming the dual structure body region portions comprising: forming a first mask on the surface of the substrate with an opening exposing the first region of the substrate; implanting through the opening a first impurity of the first conductivity type and having a first diffusion coefficient; implanting through the same opening a second impurity of the first conductivity type and having a second diffusion coefficient lower than the first diffusion coefficient; and co-diffusing the first and second impurities to form the dual structure body region portions of a field effect transistor, wherein the resulting dual structure body region portions are further processed to form the source region and the drain region.