Most vets wont' do much but give you Forbid, but yours may be different, so give him/her a call for sure! How old is your dog? I would say about 50% of puppies eat poop, and most grow out of it. 3 of our last 4 dogs ate poop, 1 has completely grown out of it, the other 2 would go through the odd phase where they would eat it as an adult, but that may have had to do with what the other dog got into that day etc....I am not sure if any of them have eaten their own, I never really looked to see who's poop they were eating!
Anyways, the very very best way to make it stop, is to clean it up as soon as they go. Yes, that means going out everytime your dog goes out and picking it up. Another thing you can try is if you can see your whole yard from the back door, stand and wait for him to go, then *as soon* as he is finished, call him to you and give him a treat. He will get used to coming to you for that treat after he poops...you have to remain consistant for this to work and do it every single time (like any kind of training). You could try shaking a shaker can when you see him do it, then call him when he stops, and reward when he comes to you (you are rewarding him coming, not eating the poop...he will have forgotton he was eating poop by the time he gets to you).
Another thing to look at is what he is eating. If he is on a high quality kibble, it isn't a nutritional deficit, however if he is on something from Wal-Mart, the grocery store etc, he might be lacking in some nutrient and it would be a good idea to switch him to a better quality food. Does he get table scraps? Maybe they still smell good the "second time around". Table scraps add nothing to his diet, so you can cut those out completely. It was interesting with my dogs...when Quest was a puppy she got Nutro L/R. She ate her poop. As she got older she was taken off puppy food adn put on chicken/rice as she developed an allergy to lamb (lesson learned, never feed L/R unless necessary!), and stopped eating poop. When we got the Vizsla he was also on Nutro L/R from the breeder. Quest ate his poop. When we switched his food a few weeks later, she stopped eating his poop. Obviously something in the food when it came back out was appetizing to her. So, maybe even if he is getting a good quality food, try one with a different protein base and see if that helps.
If you feed raw, then you might be missing a key nutrient and may want to reevaluate your diet, or talk to your vet about it. I can't say much on it, as I dont' feed raw.
Other thing, maybe he is just bored. How much exercise does he get? what type of dog is he? If he is a sporting/herding/hound breed he needs LOTS of off leash exercise, not jsut a stroll down the street on a lead.
Anyways, maybe a little more info and we could help you narrow it down a little or pinpoint some things to try.