Special size effects in advanced single-gate and multiple-gate SOI transistors

State-of-the-art SOI transistors require a very small body. This paper examines the effects of body thinning and thin-gate oxide in SOI MOSFETs on their electrical characteristics. In particular, the influence of film thickness on the interface coupling and carrier mobility is discussed. Due to coupling, the separation between the front and back channels is difficult in ultra-thin SOI MOSFETs. The implementation of the front-gate split C-V method and its limitations for determining the front- and back-channel mobility are described. The mobility in the front channel is smaller than that in the back channel due to additional Coulomb scattering. We also discuss the 3D coupling effects that occur in FinFETs with triple-gate and omega-gate configurations. In low-doped or tall fins the corner effect is suppressed. Narrow devices are virtually immune to substrate effects due to a strong lateral coupling between the two lateral sides of the gate. Short-channel effects are drastically reduced when the lateral coupling screens the drain influence.