Hi Closeyone and welcome to GoY. No you can't lay a lawn on concrete, even if there is 6 inches of soil between the concrete and the actually lawn as there would be no way for the water to drain away. You'll need to remove the concrete first.

It would be a very soggy lawn as it wouldn't drain properly so, no, it is not a good idea!!

It would also dry out very quickly. My parents garden has a 3 foot wide path along the length of their lawn but 6" under it and there's a long strip of brown grass when it gets dry.