@Tim Edwards,I found out that parasitic extraction commands in magic extract only coupling capacitors between parallel wires. I was wondering to find parasitic capacitors at nodes for a long wire drawn using any metal layer ?? Does magic extrcation commands do that??

I'm not sure what you mean by "extract only coupling capacitors between parallel wires"?

I mean .. in general parasitic extractions extracts parasitic caps across nodes of mosfet (which is not present in extracted spice file) and coupling cap. between parallel wires(which is present in extracted spice)

I'm still not getting what you're asking for.

@Deepak if i am understanding correctly you are asking why some nodes don't have a parasitic capacitance associated in the parasiti extraction netlist? May be below some threshold no capacitance is generated? @Tim Edwards

Yeah @Stefan Schippers. I have used " cthresh 0" which i think should include all capacitors.

If an extraction tool really extract all mutual capacitances above 0 you will get a huge number of capacitors, any node has a finite coupling capacitance to any other node. Don't know the answer, just curiosity.

If you're asking why MOSFET source, gate, and drain capacitances are not included in the extracted parasitics, it's because they are part of the FET model. Normally you pass the FET gate width and length, and the source and drain area and perimeter, to the FET model, and the model computes all of the capacitances internal to the device itself.