>Edit:also , they mentioned an ncfet transistor for general use.since this transistor remember his state, you may not have to power it in sleep mode(whole circuit or partial), and thus could get zero leakage current!

Um, no, that's not the point of the NC FET. The "negative capacitance" aspect of the ferroelectric material means that the NC FET can switch on or off faster, reducing power wasted in the switching process, and therefore allow chips to run cooler.

See https://phys.org/news/2011-09-ferroelectrics-pave-ultra-low-... for a general explanation or https://www2.eecs.berkeley.edu/Pubs/TechRpts/2015/EECS-2015-... for a technical explanation.