Silicon Carbide MESFETs were fabricated on n-doped substrates (N-d 4x10(18)cm(-3)), utilizing 15 mum low doped epi layers (N-d mid 10(15)cm(-3) range) for reduction of capacitive losses. An f(max) of 31 GHz and an extrinsic f(t) of 7.8 GHz for a gate length of 0.4 mum were achieved. The pad capacitances for the gate and drain contacts of the devices were 2-3 times the values of devices made on semi-insulating substrates.