Haren, acquired in an offseason trade with the Oakland Athletics, is 12-5 with a 2.75 ERA, fourth-best in the National League. He is fourth in the NL in strikeouts with 142 and leads the league in strikeout-to-walk ratio at 5.92.
"I knew I'd like it here but I didn't know I'd like it this much," Haren said at a news conference at Chase Field on Tuesday. "A lot of these guys are going to be around for a while and I'll be one of them. I just couldn't be happier."
The 27-year-old Haren is part of a potent 1-2 Arizona pitching punch with staff ace Brandon Webb, who also has had talks with the Diamondbacks on a new deal.
Haren's new deal includes $31.5 million more than he would have made in his old contract, which ran through 2009 with a team option for 2010. If the club picks up the option for 2013, the new contract would total $56.75 million.
The contract pays him $7.5 million in 2009, $8.25 million in 2010, and $12.75 million in 2011 and 2012. The deal includes a $3.5 buyout if the team doesn't pick up the option.
Webb, 16-4 after a complete-game 3-1 victory over Pittsburgh on Tuesday night, has a contract that also expires in 2009 with a club option for 2010. But Byrnes said talks on a new contract for Webb have been "tabled" for now. Webb, the NL Cy Young winner in 2006, makes $6.5 million in 2009 and, if the team picks up the option, $9.5 million in 2010, including $1 million in incentives he's already reached.
The right-handed Haren has been durable as well as effective. Since 2005, he is tied for second in the majors with 125 starts and is third in innings pitched with 816 1/3. Manager Bob Melvin said he found Haren to be better than advertised.
"I didn't realize what an intense competitor he is and what a big-game pitcher he is," Melvin said. "The better the opponent, the tougher the game, the more excited he is about pitching."
Haren and Webb were Arizona's All-Star Game representatives this year. Haren, who started the 2007 All-Star Game for the American League, pitched two scoreless innings in the contest this season in New York.
Haren, who has moved his family to nearby Scottsdale, came to Arizona along with pitcher Connor Robertson in exchange for six prospects. He has a career record of 61-49, 31-14 the past two seasons. Haren pitched in the World Series for St. Louis and was part of the rotation for the 2006 Oakland team that advanced to the division finals.
He said this Diamondbacks' team reminds him of that A's squad.