Abstract: A two stage threshold adjust implantation process is performed after field oxidation to avoid the effects of dopant redistribution and segregation. At any of several steps in a manufacturing process, only routine implant energy and dose adjustments are required to create a first and a second dopant profile (110, 120) that result in the reduction of edge leakage and threshold voltage sensitivity to device layer thickness of a semiconductor device on a semiconductor on insulator substrate.

Abstract: A method of adjusting a threshold voltage for a semiconductor device on a semiconductor on insulator substrate includes performing a threshold voltage adjustment implant (25) after formation of a gate structure (16) to reduce the diffusion of implanted dopant (26). Reducing dopant diffusion eliminates the narrow channel effect which degrades device performance. Implanting the dopant (26) after formation of the gate structure (16) simplifies processing of semiconductor device (28) by eliminating a photolithography step which is accomplished by utilizing photoresist (21) used for a source and drain implant (22).

Abstract: A varactor (10, 115, 122) is formed using a BICMOS process flow. An N well (28) of a varactor region (13) is formed in an epitaxial layer (22) by doping the epitaxial layer (22) with an N type dopant. A cathode region (55, 132) is formed in the N well (28) by further doping the N well (28) with the N type dopant. Cathode electrodes (91, 114) are formed by patterning a layer of polysilicon (62, 86) over the epitaxial layer (22). Subsequently, the cathode electrodes (91, 114) are doped with an N type dopant. A region adjacent the cathode region (55, 132) is doped to form a lightly doped region (103, 117). The lightly doped region (103, 117) is doped with a P type dopant to form an anode region (109, 119).