Ultralow-voltage (ULV) CMOS will be a core building block of highly energy efficient electronics. Although the near-or sub-Vth operation is effective in reducing energy per operation of CMOS circuits, its slow operation speed can miss a chance to be used in many applications. The silicon-on-thin-buried-oxide (SOTB) CMOS is a strong candidate for the ul-tralow-power (ULP) electronics because of its small variability and back-bias control. This paper describes our results on the ULV operation of SRAM and ring oscillator (RO) circuits and shows the operation speed is now sufficiently high for many ULP applications. The 'Perpetuum-Mobile' micro-controllers operating at ∼0.4 V are expected to be implemented in many applications such as the internet of things.