An n-well CMOS with self-aligned channel stops

A new n-well CMOS structure is described in which the performance of the n-channel MOSFETs can be optimized. This structure also provides self-aligned channel stops to offer rigorous isolation for high density ICs. A novel process was developed to fabricate the structure. Extremely low body effect coefficients (γ=0.1-0.2) are obtained from the resulting n-channel MOSFETs with 1.25µm channel length. Moreover even at 10V, subthreshold currents in the isolation region between two similar or two opposite type FETs are < 1 pA.