High frequency characterization of gate resistance in RF MOSFETs

The gate resistzances (R-g) of MOSFETs with various geometries have been characterized at various bias conditions at high frequency (HF), The results show that R-g decreases when either channel length (Lf) or per-finger-width (W-f) increases before reaching a critical L-f or W-f, and then starts to increase as Lf or W-f continues to increase. The irregular geometry dependence of R-g is caused bg; the combined distributed effects in bath the gate and channel at HF,Stronger contribution from the distributed channel to the effective R-g is observed in the saturation region of devices with longer channel length (L-f) at lower gate bias (V-gs). The results show that an optimized design of the per-finger-width is necessary for an rf MOSFET to achieve the lowest effective R-g,R- which is desirable in rf applications.