The scale down of device dimension is an effective way to realize VLSI technology
however
the dimension is limited to a definite level by the influence of some parasitic and second order effects. On the basis of comparative analysis of small devices operating at room temperature and at low temperatures
the subthreshold behaviour and its effects on the device properties and scale downprinciples are described emphatically. A kind of low temperature scale down principle is presented according to the low temperature operation characteristics
which will play an important role in low temperature MOSFET optimal design and further improvement of the circuits and systems.