You have had some good responses, thought I would add my 2 cents. First off, I always laugh at parents who believe the child should direct their sleeping habits and the parent is just merely an observer. As a parent, it is not only advised, but our job to direct and steer the child torwards good sleeping habits.
I agree with the mom who advised adjusting the baby's formula. I, however, didn't decrease the amount of formula, I started adding water to it to water it down. I still heated it, just like before, but I gradually added water to thin it out. After about 4-5 days, it was basically all water and the baby stopped waking up, why bother.
Lastly, watch out with loading the baby down with tons of food before they go to sleep. I had 2 kids who woke up more often with more food. You know how when you go to bed just stuffed and then wake up early starving, this would happen to my kids. Increase that last feeding a little bit, not too much. Good luck, be consistent and believe it will happen and soon.