"I knew I'd like it here," said Haren, who was acquired from the A's for six prospects. "I've said before I didn't know I'd like it this much. The guys have been great, the team is exciting to watch and it's fun to have them play behind me."
In 23 starts this year, Haren is 12-5 with a 2.75 ERA, the fourth-best mark in the National League.
"He's been everything we had hoped for and more," D-backs GM Josh Byrnes said. "His performance has even gone to a higher level. I think the most impressive thing about him is the motivation for winning."
Haren, who will turn 28 next month, was initially under contract through 2009 with a team option for 2010. That contract no longer exists, as the new one is for 2009 through 2012 with a team option for 2013.
The deal calls for $7.5 million next year, $8.25 million in 2010 and $12.75 million each in 2011 and 2012. The team option is for $15.5 million, and if the D-backs choose not to pick it up they must pay a $3.5 million buyout.
"I'm not the mentality kind of guy that wants to go cash it in and make a huge, just ridiculous contract," said Haren, who would have earned $5.5 million next year and $6.75 million in 2010 under his old deal. "I'm comfortable here, and I wanted to be here. I wanted to talk, and I wanted to stay here."
Arizona manager Bob Melvin had seen plenty of Haren before he came to the D-backs but has been surprised by some things he's learned about him.
"I didn't realize what an intense competitor he is and what a big-game pitcher he is," Melvin said, citing the way Haren pitched against the Red Sox in Fenway Park earlier this year. "The better the opponent, the tougher the game, the more excited he is about pitching. It's just about competing for him. It's not about the money."
Haren, along with teammate Brandon Webb, gives the D-backs one of the best one-two punches in the game.
"What I hoped for was to make things a little easier for him," Haren said. "I wanted to try and take a little pressure off him because I knew he would take pressure off me with the way he's thrown the ball the last couple of years. It's great having him in the rotation. He's a true staff ace."
The talks with Haren had been going on for quite a while, and the two sides reached agreement just prior to leaving on their recent 10-game road trip.
With the D-backs having a young core of position players as well as Webb tied up through 2010, Haren has a good idea of what the team will look like for years to come, and that was one of his motivations in signing the deal.
"The guys really care for each other and pick each other up," he said. "It's been fun to see the way we've come back -- especially the last few weeks -- and played so well. The guys really got together, and we all have one goal to win this division."