I agree pretty much with WittyKitty. Keep placing him in the litter tray when he wakes and after he eats. Clean the affected area with biological detergent. Have you tried a different sort of litter - he may not necessarily like the type you have. If you have clumping try a non-clumping or vice versa and/or hooded tray if you have an open tray.

Good luck, I hope you resolve the issue.