Bulk cmos rf switch with reduced parasitic capacitance

Abstract

Bulk CMOS RF switches having reduced parasitic capacitance are achieved by reducing the size and/or doping concentration of the switch's N-doped tap (N-Tap) element, which is used to conduct a bias voltage to a Deep N-Well disposed under each switch's P-Type body implant (P-Well). Both the P-Well and the N-Tap extend between an upper epitaxial silicon surface and an upper boundary of the Deep N-well. A low-doping-concentration approach utilizes intrinsic (lightly doped) N-type epitaxial material to provide a body region of the N-Tap element, whereby an N+ surface contact diffusion is separated from an underlying section of the Deep N-well by a region of intrinsic epitaxial silicon. An alternative reduced-size approach utilizes an open-ring deep trench isolation structure that surrounds the active switch region (e.g., the Deep N-well and P-Well), and includes a relatively small-sized N-Tap region formed in an open corner region of the isolation structure.