A Comprehensive Study of High- $Q$ Island-Gate Varactors (IGVs) for CMOS Millimeter-Wave Applications

This paper presents a comprehensive study on the high-
$Q$
island-gate varactor (IGV), which includes a comparison with the conventional multifinger varactors (MFVs) and analyses on the effect of structural variations on the varactor performance. The study shows that the IGV exhibits smaller
$R_{s}$
and larger
$Q$
factor compared to the MFV, while its capacitance tuning ratio is smaller. The effect of the dimension variation and shape of the gate island, as well as the gate thickness, is substantial and the observed trends can be exploited for IGV optimization. This work indicates that the IGV is a highly promising option for millimeter-wave applications.