Reverse Short-Channel Effect of Body Factor in Low-Fin Field-Effect Transistors Induced by Corner Effect

The impact of Fin-corner shape on the body factor γ of low-Fin (tri-gate) field-effect transistors (FETs) in both cases of highly doped channel and undoped channel has been investigated by three-dimensional device simulation. The behaviors of both threshold voltage (V th) and γ depend on whether V th is derived from on-state or off-state characteristics. In highly doped low-Fin FETs, γ derived from off-state characteristics (γI0) is strongly affected by corner shape, and the increase in γI0 with the reduction in gate length (reverse short-channel effect of γ) due to the corner effect has been observed in devices with sharp corners. The variation in off-current due to gate length fluctuation can be suppressed by applying a negative substrate bias thanks to the reverse short-channel effect of γ in highly doped low-Fin FETs with sharp corners. On the other hand, in undoped low-Fin FETs, the corner shape dependence is weaker and short-channel characteristics become considerably worse than those in highly doped FETs.