Try taking away his water around 7-8 PM unless it's really hot out. Also, I find that mine sleep better and longer if they have a little something in their tummies-maybe give him a few treats or a spoonful of cottage cheese around 9 pm? Finally, try putting a t-shirt or a pair of pajamas on him. I don't know why, but this has helped Milli too.
I've had the same problem, and until a few weeks ago, hadn't slept through a whole night since Feb 21! Milli's now 8 months old, and still wakes up
If she wakes up early though and cries/barks, I put her in her crate downstairs, and she stays there until I get up-but I get up early-5-6 am.