Ultralow Specific On-Resistance High-Voltage SOI Lateral MOSFET

An ultralow specific on-resistance (
R
_on,sp
) integrable silicon-on-insulator (SOI) power lateral MOSFET is proposed. The MOSFET features double trenches: an oxide trench in the drift region and a trench gate extended to the buried oxide (BOX) (SOI DT MOSFET). First, the oxide trench causes multiple-directional depletion, which leads to electric field reshaping and an enhanced reduced surface field effect in the SOI layer. The electric field distributions in the SOI and BOX are thus improved. The oxide trench also increases the electric field strength in the
x
-direction due to the lower permittivity of oxide than that of Si. Both increase breakdown voltage (BV). Second, the trench makes the drift region folded in the
y
-direction, resulting in reduced cell pitch and
R
_on,sp
. Third, the trench gate extended to the BOX further reduces
R
_on,sp
by widening the vertical conduction area. The BV of the DT MOSFET increases from 91 V of the conventional SOI LDMOS to 233 V at a half-cell pitch of 6.5 μm, and the
R
_on,sp
decreases from 5.1 to 3.3 mΩ·cm
²
.