If you're referring to this graph [1], that comes from an ITRS prediction. These predictions seem to be made assuming that we'll scale feature sizes assuming everything else will stay the same, which of course, is never the case. I wouldn't read too much into them. BTW, ITRS is famous for making ridiculous predictions like we'll using 15GHz by 2011.
Why is it not an effective knob? Most modern designs include sleep transistors in an attempt to not leak when a circuit is inactive. These would not work unless we could engineer high-vt transistors.
[1] http://www.eetimes.com/ContentEETimes/Images/Design/Prog%20L....
Threshold voltage is not really an effective knob
Why is it not an effective knob? Most modern designs include sleep transistors in an attempt to not leak when a circuit is inactive. These would not work unless we could engineer high-vt transistors.