Anaheim, second in the division, has three games remaining and trails San Jose by eight points. The Ducks had won 10 straight at home.
The Sharks won their third division crown and first since the 2002-03 season. They also finished first in the 2001-02 campaign. San Jose has points in 18 straight games (16-0-2).
Boucher shut out the Ducks after the first period, and Jeremy Roenick and Curtis Brown scored second-period goals for the Sharks.
Boucher has allowed just three goals in four games since being signed by the Sharks on Feb. 26.
Anaheim rookie Jonas Hiller stopped 24 shots as he played his fourth straight game in place of Jean-Sebastien Giguere, who has been sidelined by back spasms.
Roenick snapped a 1-1 tie at 11:10 of the second period, and Brown gave the Sharks a two-goal pad six minutes later.
Roenick scored his 14th goal during a power play. Parked near the left post when he got the puck, Roenick knocked it past Hiller during a delayed second penalty call on Samuel Pahlsson.
Brown picked up a loose puck just to the left of the crease and poked it past the sprawling Hiller for his third goal.
The Sharks' Patrick Marleau opened the scoring when he wristed a shot past Hiller at 6:38 of the first period, his 17th goal. Scott Niedermayer evened it at 11:09 of the period with a slap shot down the slot that sailed through a crowd in front. It was Niedermayer's eighth of the season.
