Improved RF Performance with Buried Power Rail and Contact over Active Gate in Nanosheet FETs

This paper provides an in-depth exploration of an RF device technology developed on the nanosheet FET (NSFET) platform. A buried power rail (BPR) RF device layout delivers an impressive cut-off frequency (Ft) / maximum oscillation frequency (Fmax) ratio of 535/610 GHz. Moreover, when optimizing the BPR structure and combining it with the Contact over Active-Gate (COAG) structure, remarkable results are achieved, with Ft/Fmax reaching 532/699 GHz. Notably, this proposed COAG mix BPR design effectively reduces gate resistance while improving Fmax by approximately 50% compared to the baseline structure, all while maintaining performance levels equal to the latter.