Memory cell having active regions without n+ implants

Abstract

Lightly doped active regions in a semiconductor structure reduce occurrences of pipeline defects. The light doped active region are typically employed where performance is not adversely affected. For example, in memory cells, pass transistors have lightly doped drains which directly connect to bit lines. A pass transistor of this type can have the source more heavily doped than the drain. Alternatively, drains and sources of pass transistors are lightly doped. Drains of pull-down transistors can also be lightly doped. The difference in doping of active regions does not increase fabrication processing steps because conventionally active regions are formed by two doping steps to create a lightly doped portions adjacent gates where field strength is highest. The invention changes such processes by covering the desired lightly active regions with the mask used during a second doping process.