relation between Vt and width of transistor

With decrease in width VT will increase

With decrease in Length VT will increase, But both the variation will be less, when you will go to sub micron 0.45 um, this variation will be more,

so also if you use larger channel length, there will be less variation with width compared to small channel length

Re: Relation between Vt and width of transistor

VT decreases with increase in width, The reason behind this behavior is short channel effect, The channel charge is controlled by the source and drains partly making the actual channel charge inversion and depletion charge controlled by the gate becoming trapezoidal hence reduction in Vt. However this thing is exactly along the width direction. If you see the device cross section along the width, the gate has to control the channel charge of trapezoidal area but top edge equal to that of width of the device and bottom edge of more than the device width. Hence the total charge controlled is more hence higher Vt. This is mainly due to birds beak present hence the thickness of the gate oxide at the edges will be more. which increases Vt.