Design and Fabrication of Asymmetric MOSFETs Using a Novel Self-Aligned Structure

Abstract—A novel asymmetric MOSFET with no lightly doped drain on the source side is simulated on bulk Si using a device simulator (SILVACO). To overcome the problems of the conven-tional asymmetric process, a novel asymmetric MOSFET using a mesa structure and a sidewall spacer gate is proposed, and it provides a self-alignment process, aggressive scaling, and better uniformity. First of all, we have compared the simulated character-istics of the asymmetric and symmetric MOSFETs. Basically, both asymmetric and symmetric MOSFETs have an n-type channel and the same physical parameters. Compared with the symmetric MOSFET, the asymmetric MOSFET shows better device perfor-mance. Moreover, we have successfully fabricated 50-nm asym-metric NMOSFETs based on simulation results and investigated its operation and characteristics. Index Terms—Asymmetric MOSFET, lightly doped drain (LDD), mesa structure, sidewall spacer gate. I