How deep to repot young coriander and basil plants

I think my coriander and basil seedlings are now ready to pot up from their current seed tray home. Question is how deep I should plant their stems? The coriander plants have about 6cm between top of soil and seed leaves, and basil around 8cm. Can both coriander and basil stems be buried up to their seed leaves? My coriander also seems to have produced two stems from each seed; do I treat each set as a single plant? I'll grow all on until I plant out end of May/June time.