Analysis and modeling of a MOS transistor with long gate finger for millimeter wave band applications

Performance of a MOS transistor is drastically degraded in millimeter wave bend, in the case of long finger lengths. The reason is Longitudinal Distributed Effect (LDE) along the gate finger. LDE has been modeled in new commercially used (e.g. BSIM4) or under develop (e.g. BSIM6) RF-CMOS transistor models. An approximated approach has been used in these models that causes to considerable errors in the case of long finger lengths. In this paper we propose a new small signal model that accurately captures LDE in the case of long finger gates. The proposed model has been validated using the foundry design kit for TSMC 90nm RF CMOS technology.