double gate mos wikipedia
Double gate is comprised of conducting channel which is usually undoped and surrounded by gate electrodes on their sides just to ensure that no part of channel is far away from a gate electrode.
The voltage applied on the gate terminal control the elctric field determing the ammount of current flow through the channel.
its advantage is that undoped channel eliminates intrinsic parameter fluctuation and minimizes impurity scattering
also it can drive higher current..and also the reduction of drain current..
Hope it helps you...