Is it more appropriate to run Monte Carlo simulation on circuit schematic or on the post-layout extracted version?
Will the mismatches be captured more realistically if the analysis is run on the post-layout extracted version?
There are three reasons why it may be more accurate, but I suspect these are not the effects you are thinking of:
I suspect you are wondering whether the effects of good layout matching will be taken into account. Well, the random monte carlo variation is generally capturing the remaining random variation, and not systematic variation due to layout proximity and alignment. If there was some element of that included in the variation of the devices, there might be some benefit in providing some information about the correlation between the devices, but:
That said, using capabilities such as mismatch contribution in ADE Explorer/Assembler (a Virtuoso Variation Option feature, or as an ADE GXL feature when using ADE XL) can help identify the variation of which devices contributes most to the variation of the output, and typically these will be the devices for which you need to take greater care on for matching to ensure that all you're getting is the remaining local random variation and not systematic variation due to poor layout.
So post-layout statistical simulation will be useful (although it will often be slower of course, especially if you have parasitics).
Hope that helps!
THANK YOU very much Andrew for that detailed and very insightful reply. It surely helps