Double-gate MOSFETs: performance and technology options

The advantages of double-gate (DG) SOI MOSFETs over conventional, single-gate transistors are described in terms of performance and potential for ultimate scaling. The peculiarity of DG-MOSFETs is that the top and bottom gates are biased simultaneously to establish equal surface potentials: V/sub G2/ = V/sub G1/ for identical gate oxides, or V/sub G2/ = V/sub G1/(t/sub 0X2//t/sub 0X1/) to compensate for the difference in front and back oxide thickness. In fully depleted transistors with a thin enough film, controlling the channel from both sides, forces most of the carriers to flow in the middle of the film, according to the volume inversion concept. Volume inversion results in excellent properties, which will be reviewed in this paper. In particular, the carrier mobility is enhanced, so that the transconductance in double-gate mode exceeds twice the value observed in single-gate mode. A DGMOSFET is more than the sum of two classical transistors.