Ofcourse, There is leakage current in MOSFET and it plays important role in deciding power consumption of circuit. Leakage current consist many consists of many components.
1. Leakage through gate oxide
2. Current through reverse biased source-bulk, drain-bulk junctions.
3. Sub-threshold conduction
Upto what extent i can decrease/increase my oxide thickness . if i make it thicker , electric field penetration would be less . but if i make it thin , leakage current incs. how to come up with right area of oxide . Using 90nm technology.
At 90 nm, reverse bulk diode biasing will reduce leakage during standby modes. Obvious other alternative is to power gate circuits not in active clocking. You can also employ dual threshold process option. Low threshold devices for speed, higher threshold for low leakage. You can combine the later two to transfer high speed memory to low leakage memory backup during standby and restore upon wake up.