Leakge current in low Vt cells

[riti]

Why leakage current in low Vt cells is high as compare to high Vt cells ?

[dick_freebird]

Because the subthreshold slope has not intersected the
junction leakage floor by the time you hit Vgs=0.

This not only makes the leakage higher, it makes it highly
variable - a nominal 80mV/decade means that if your VT
of 200mV (low-VT) has a +/-100mV tolerance the real
leakage current could vary upward by over a decade at
Vgs=0 (or downward, but nobody cries about that).
And even at nominal, 2.5 decades (for 200mV/80mV)
means you'd leak about 3nA per transistor (where a
good long channel high VT FET should be femtoamp
range). Now figure your LVT transistor count.

[ThisIsNotSam]

Why leakage current in low Vt cells is high as compare to high Vt cells ?

Simply put, because low Vt cells are designed for performance. The trade-off is that the threshold is so low/narrow, that it leaks more.