Circuits, integrated circuits devices, and methods are disclosed that may include biasable transistors with screening regions positioned below a gate and separated from the gate by a semiconductor layer. Bias voltages can be applied to such screening regions to optimize multiple performance features, such as speed and current leakage. Particular embodiments can include biased sections coupled between a high power supply voltage and a low power supply voltage, each having biasable transistors. One or more generation circuits can generate multiple bias voltages. A bias control section can couple one of the different bias voltages to screening regions of biasable transistors to provide a minimum speed and lowest current leakage for such a minimum speed.