Planar Process : creating 3-D devices using 2-D process . i.e. by depositing layers on one another.
3.1 Layering
Between every 2 active layers ( i.e. layers of metal )  there is an insulating layer.
Photo lithography: A process used to transfer patterns to the Silicon wafer.
Three Important Rules
1. minimum width
For very small
width you may
have a fuse
2. minimum separation
3. Minimum overlap
Source and Drain may
be connected