Oxidized-Silicon-Terminated Diamond p-FETs With SiO2-Filling Shallow Trench Isolation Structures

Herein, excellent electrical performances were achieved for the oxidized-silicon-terminated (C–Si–O) diamond metal–oxide–semiconductor field-effect transistors (MOSFETs) using chemical-vapor-deposition grown SiO2 as the filling insulator of shallow-trench-isolation (STI) structures and gate oxide. The C–Si–O interface was formed under the initial SiO2 layer (
$1^{\text {st}}$
SiO
$_{{2}}{)}$
as a mask during heavily boron-doping growth. The surface carbon-rich layer formed on the mask during selective diamond regrowth was removed using the oxygen plasma ashing treatment. The device having a 130-nm-thick SiO2 gate insulator exhibited subthreshold slopes (S S) of 220–710 mV/dec between 473 and 673 K. A normally-off operation was confirmed at 673 K. The SiO2filling insulator (
$2^{\text {nd}}$
SiO
$_{{2}}{)}$
containing positive fixed charges can block the hole transport channels, and the active regions of the device are out of one plane using the STI structures. Accordingly, OFF-state drain leakage current was successfully suppressed. Consequently, high on–off ratios of
$10^{{6}}$
–
$10^{{7}}$
that cannot be realized in hydrogen-terminated (C–H) diamond FETs were confirmed up to 673 K. To summarize, results of this study provide new strategies for advancing diamond devices from the laboratory to industrial applications.