Inventors:
Robert R. Doering - Plano TX
Michael P. Duane - Houston TX
Gregory J. Armstrong - Houston TX
Assignee:
Texas Instruments Incorporated - Dallas TX
International Classification:
H01L 21265
H01L 2978
H01L 2704
Abstract:
A semiconductor device such as a dynamic read/write memory or the like is made by a twin-well CMOS process that employs a minimum number of photomasks. Field oxide isolation areas are formed in nitride-framed recesses so a relatively plane surface is provided, and a minimum of encroachment occurs. Both P-channel and N-channel transistors are constructed with silicided, ion-implanted, source/drain regions, self-aligned to the gates, employing an implant after sidewall oxide is in place, providing lightly-doped drains. The threshold voltages of the P-channel and N-channel transistors are established by the tank implants rather than by separate ion-implant steps for threshold adjust.