STRUCTURE AND FABRICATION OF ASYMMETRIC FIELD-EFFECT TRANSISTOR HAVING ASYMMETRIC CHANNEL ZONE AND DIFFERENTLY CONFIGURED SOURCE/DRAIN EXTENSIONS

摘要

An asymmetric insulated-gate field-effect transistor (100) has a source (240) and a drain (242) laterally separated by a channel zone (244) of body material (180) of a semiconductor body. A gate electrode (262) overlies a gate dielectric layer (260) above the channel zone. A more heavily doped pocket portion (250) of the body material extends largely along only the source. Each of the source and drain has a main portion (240M or 242M) and a more lightly doped lateral extension (240E or 242E). The drain extension is more lightly doped than the source extension. The maximum concentration of the semiconductor dopant defining the two extensions occurs deeper in the drain extension than in the source extension. Additionally or alternatively, the drain extension extends further laterally below the gate electrode than the source extension. These features enable the threshold voltage to be highly stable with operational time.