Calvin Stengs has been rewarded after a couple of impressive outings for AZ with a five-year contract at the Eredivisie side.
The 18-year-old Dutch footballer excelled for the club in their two European play-offs where he scored a goal in each of the two legs against Groningen.
He also provided an assist as the club progressed 8-2 on aggregate after two 4-1 wins.
Stengs, who scored six goals in 22 games for the club's Second Division side, told the clubs official website: "I have a good season and this is the reward for it."
AZ have since defeated Utrecht 3-0 in the first leg of the two-legged final and will be hoping to finish the job when second leg of the play-off takes place on Sunday.