Substrate-induced high-frequency noise in deep sub-micron MOSFETs for RF applications

We present results from high-frequency noise measurements on NMOS devices fabricated in a 0.5-/spl mu/m epi-based CMOS process. These noise measurements at RF frequencies reveal the existence of substrate-induced high-frequency noise in transistors operating in the saturation regime. The substrate-induced noise is independent of the transistor bias conditions, but is strongly dependent on the geometry of the device and the MOS gate-to-bulk capacitance. A new ac noise model for CMOS devices operating at RF frequencies presented here shows good conformity to measurements. Its implications are emphasized via the design of a low-noise amplifier (LNA) operating at 2 GHz. The minimum achievable noise-figure (NF) can be higher by as much as 0.6 dB due to this substrate-induced high-frequency noise.