Graded gate VDMOSFET

In this work, we present a novel RF VDMOSFET with graded gate structure. It can be fabricated by regrowing gate oxide after gate patterning. This structure enables a very thin gate oxide to be used in the channel region; thus a much high transconductance can be obtained. At the gate edges, the gate oxide thickness increases smoothly to about three times that of the channel region. This releases the electric field crowding at the gate edge, improving the breakdown voltage from 24 V to 68 V.