transistor sizing

Why is that when we size the transistor we vary the width and not the length..? I am new to vlsi..so pl excuse me if its a basic question.

the transistor sizing is done only to the width of the transistor not for the length, the length is fixed based on the technology. If it is 90nm then the length of the transistor is 90nm so it is fixed for the transistor in that 90nm technology no varying is done.

I t is not like that .. actually.... the basic digital blocks are designed with basic length,,,,

But if u need you can change length too... Example current mirror...

In current mirrors, the more appropriate current mirroring is achieved at particular lenght of the device... In that case we fix the length other than minimum size...

But, after fixing length for a current mirror, we just change the width or multiplier to get multiplication of current...

Thanks

This link is very Helpfull..
https://bit.ly/IThCZA