Highly tunable metal-on-semiconductor varactor

Abstract

A metal-on-semiconductor varactor with a high value of Cmax/Cmin comprises a semiconductor bottom plate with an array of semiconductor pillars. The pillars may be in an accumulation mode to provide a high capacitance or in a depletion mode to provide a low capacitance. The maximum capacitance in an accumulation mode is primarily determined by the capacitance of the semiconductor pillars. The minimum capacitance in a depletion mode is primarily determined by a capacitor formed on an inter-pillar semiconductor surface between the semiconductor pillars. The minimum capacitance, and hence the value of Cmax/Cmin may be tuned by adjusting process parameters, design parameters and by alterations in the MOS varactor structure such as forming a highly doped semiconductor layer beneath the inter-pillar semiconductor surface or forming a plate insulator.

Dependencies are inferred from the claim text.