Plíšková was playing in her first event since moving to the top of the world rankings last month.
The sixth seed was able to comfortably get the better of Stephens, who can take great heart from reaching the semis in only her third tournament of an injury-plagued campaign. But her efforts were undone by too many unforced errors and Wozniacki calmly marched through the first set.
EPA/WARREN TODACaroline Wozniacki of Denmark celebrates her win over Sloane Stephens of the us after their semi-final match in the Rogers Cup Women's Tennis tournament in Toronto, Canada, 12 August 2017. But Wozniacki struck again a few games later, and served out the match after a brief rain delay at 5-3.
Halep defeated Frenchwoman Caroline Garcia 6-4, 6-2 while fifth seeded Svitolina rallied from a first set loss to beat reigning Wimbledon champion Garbine Muguruza 4-6, 6-4, 6-3.
Denmark's Caroline Wozniacki has advanced to the Rogers Cup final.
After beating Spain's Rafael Nadal yesterday, the 18-year-old wild card entry overcame Frenchman Adrian Mannarino 2-6, 6-3, 6-4. She'll face either Elina Svitolina or Simona Halep for the title. But I think I'm ready, I feel strong enough in my legs.