The boron-doped diamond (B-diamond) metal-oxide–semiconductor field–effect transistors (MOSFETs) are fabricated and characterized at operating temperatures up to 400°C. The SiO

2

serves as the gate oxide insulator

while the Ti/Pt bilayer is employed as the gate contact metal. As the operating temperature rises from room temperature (RT) to 400°C

the absolute drain current maximum for the B-diamond MOSFET increases from 3.9 μA mm

−1

to 177.4 μA mm

−1

. Conversely

the on-resistance decreases significantly from 1469.8 kΩ mm to 16.5 kΩ mm. The on/off ratio for the MOSFET at RT is 1.9 × 10

5

which increases to over 5.0 × 10

6

at temperatures exceeding 100°C. The threshold voltage exhibits a decreasing trend

though it deviates from this trend at 300°C. The subthreshold voltage and extrinsic transconductance maximum show increasing trends from 113 mV dec

−1

to 299 mV dec

−1

and from 0.9 μS mm

−1

to 23.1 μS mm

−1

respectively. The inter

facial trapped charge density is found to be stable in the range of 8.0 × 10

11

–2.3 × 10

12

 eV

−1 

cm

−2

.