MTCMOS techology :
Sub-threshold leakage of a transistor is the leakage current flowing through the transistor when it is turned off. In a perfect switch, such as your light switch, when it is turned off, there is no current flowing through it, and the light bulb does not glow. If the switch is bad, then even though it is turned off there could be some residual current flowing through it, which may be so small that the light bulb does not seem to glow, but its there. Modern transistors are analogous to these bad light switches, they leak when they are turned off. And to make it worse, Moore’s Law allows you to double these bad switches every two years, exponentially increasing the leakage every two years, and now it is becoming noticeable.
Thus MTCMOS are leakage solution !