The impact of layout dependent stress and gate resistance on high frequency performance and noise in multifinger and donut MOSFETs

The impact of STI stress on mobility and resulted transconductance (g_m) degradation appear as a penalty of multi-finger devices for RF and analog design. Donut device layout is proposed to eliminate the STI transverse stress and achieve higher g_m. Both NMOS and PMOS can benefit from the donut layout, with higher cut-off frequency (f_T). However, the layout dependence of g_m and gate resistance (R_g) becomes a critical trade-off in determining high frequency performance other than f_T, such as maximum oscillation frequency (f_max) and RF noise. In this paper, a comparison between multi-finger and donut MOSFETs in terms of f_T, f_max, and NF_min can provide a useful guideline of device layout for RF design using nanoscale CMOS technology.