The 29-year-old used her claycourt experience to perfect effect to secure victory in 80 minutes and become the first Italian woman in the Open era to reach the last four of a Grand Slam event.
Wozniacki, the youngest of the women's quarter-finalists, seemed to be struggling with her movement and the 19-year-old was guilty of too many unforced errors.
Schiavone, the 17th seed, took full advantage with three service breaks in the first set and after breaking for 5-3 in the second she completed victory with a superb smash.
Dementieva beats Petrova
Elena Dementieva recovered from a sticky start to beat fellow Russian Nadia Petrova and reach the semi-finals of the French Open on Tuesday.
The two baseliners renewed a professional rivalry dating back to 1997 on a rainy Court Suzanne Lenglen and it was fifth seed Dementieva who played the sharper tennis after losing the opening three games to record a 2-6, 6-2, 6-0 victory.
Both players received treatment for thigh injuries midway through the opening set and Petrova, who knocked out Venus Williams in the previous round, needed more attention after Dementieva levelled the match.
A confident Dementieva cruised through the deciding set as Petrova struggled to move properly, wrapping up victory with a forehand down the line after two hours and five minutes.
The 28-year-old Dementieva has now reached nine semi-finals but is yet to win one of the four Grand Slams. She faces Italy's Francesca Schiavone in the last four.
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