Contents I. Introduction
The gate capacitance extracted from MOS capacitor structures can be used for estimating the oxide thickness, oxide charge, and substrate doping. In recent years, the continued decrease of the gate dielectric thickness in MOS devices has made it increasingly difficult to obtain an accurate thickness value from capacitance–voltage (–) analysis due to a dramatic increase of direct tunneling current through the dielectric layer [1], [2]. To accurately extract the gate capacitance of very leaky dielectric MOSFETs, several studies were proposed [3]–[7]. The conventional low-frequency extraction using the meter (up to 1 MHz for Agilent 4284) with two-element models (parallel and series) can cause errors due to low quality factor. At high frequency (up to 110 MHz for Agilent 4294 impedance analyzer), two-element and three-element methods are used to obtain the gate capacitance. However, when the gate leakage current goes beyond or , the megahertz frequency measurement needs to be examined carefully. The use of -parameters to extract model parameters for III-V compound FETs and bipolar transistors as well as silicon MOSFETs was published [8]–[14]. This letter uses the existing -parameter measurement concept to evaluate a radio-frequency (RF) capacitance measurement, sets its lower and upper boundaries, and extracts the gate capacitance of SOI devices at the gigahertz range.
