Couture was already scheduled to make about $1.25 million this season and could have been a restricted free agent next summer. Instead, he will get paid $2.75 million in 2012-13 and $3 million in the final year of the contract.
"We reached a number that was fair to both sides," Couture said. "I want to play in San Jose, I want to stay there and I want to win there. I was happy to get the deal done."
The 22-year-old Couture was a finalist this past season for the Calder Trophy that goes to the NHL's top rookie, losing out to Carolina's Jeff Skinner.
Couture was second on the team to Patrick Marleau with 32 goals and added 24 assists to help the Sharks win their fourth straight Pacific Division title.
Couture finished second among all NHL rookies in goals and points, and ranked first with eight game-winning goals, 10 power-play goals and 235 shots on goal.
Couture added seven goals and seven assists in the postseason as the Sharks made it to the Western Conference final for the second straight season. San Jose lost to Vancouver in five games.
"Obviously, it was a successful year last year for myself," Couture said. "My goal coming into this year is to improve as a player. I'm not looking at specific statistical numbers. I want to improve my all-around game, be better on the penalty kill. I still want to score goals and points, but I want to just improve as a player."
With this deal in place, the Sharks have their top two forward lines, top two defensive pairings and starting goalie Antti Niemi under contract through the 2012-13 season as general manager Doug Wilson has made a priority of keeping his best players.
The Sharks signed long-term deals with Marleau and Joe Pavelski last offseason, kept captain Joe Thornton off the open market by giving him an extension through the 2013-14 season last October, gave Niemi a four-year deal in March before he could become a free agent and signed newly acquired All-Star defenseman Brent Burns to a five-year extension earlier this month.
"I'm just excited to get back to the team with the changes we made," Couture said. "We're definitely a better team."
Couture has quickly developed into one of the core players. He carried the Sharks during a sluggish first half last season, making sure San Jose didn't fall too far out of the playoff picture. Couture had eight game-winning goals in his first 51 games, excelling on the second line with Ryane Clowe.
With Devin Setoguchi traded to Minnesota earlier this offseason, Couture could get an opportunity to play as a wing on the top line with Thornton and Marleau next season or remain the second-line center.
Couture also played 25 games in 2009-10, recording five goals and four assists. He added four playoff goals that season.
"Logan is an excellent teammate and he proved it by committing to the team-first philosophy that we have instilled here," Wilson said. "Last season, as a rookie, he was a catalyst for our hockey club as one of our most consistent players. Over the last two postseasons, he has been one of our most reliable players. We're excited to see him build upon his early success and continue his growth over the next three seasons."