Re: what is different between the actual width and original
i can't tell much about enroachment, but the reason why the actual width is less than the design width is because the implantation of the n/p drain and source diffuses outward. some of it gets under the gate in the process. this lowers the width of the gate. another thing is that some process specifically introduce a small overlap under the gate to prevent 'hot electron' effect. this is lighter doped compared to the drain/source.