Hi. Does your son have a lovey (like a blanket or a stuffed animal). That might help him to feel more 'secure' at night when eh wakes up. he is probably just having separation anxiety. he wants to know that you are close to him when he wakes up alone and scared. does he have a nightlight in his room?
At 11 months, he is probably crawling, pulling up, maybe even walking...so he's got lots of new tricks to try out all night long.
With both of my children (Allie is now 3.5yo and Ryan is 2yo), i had to let them cry. With Ryan, he did cry on and off all night for about 3 weeks. it was horrible...but then one night it just 'clicked' for him that i wasn't going in there.
Have you tried offering him a bottle of water? or slowly watering down his formula? If he wakes up and he is only getting water, he might stop waking because it's not 'worth it' for him.
You can try Ferber too. He has many books...but basically if your son wakes and starts crying, you let him cry for 15 minutes. Then you go in, pat him, say 'it's night night time' and then leave. Don't pick him up. dont' stay in there too long. Wait 10 minutes, go back in...repeat. it might be 40x that you are going in there at first...but it should get better. Or you can sit next to his crib in a chair and pat him, but don't pick him up. then move your chair a little further away each night until you are out of the room.
Having gone through this with both children, the only thing that worked for us was to let them cry. As soon as my husband or I went in teh room, they screamed even louder. I knew they were not hungry. It was miserable to listen to them cry all night...but it got better.
Good luck!
C.