Second seed Karolina Pliskova ended French title hopes at Roland Garros for another year with a 7-6 (7/3) 6-4 victory over Caroline Garcia.
The Czech does not like clay and had won only two matches in five previous visits to the French capital.
Pliskova said: "Still before this tournament I was struggling on clay with almost everything. I didn't have my weapons on my side and the movement was terrible.
"I don't think it's better, but somehow I'm just winning. Today I can finally say I felt a little bit better on the court compared to the last matches."
There is more than just a place in the French Open final at stake, with both Pliskova and her semi-final opponent Simona Halep also going for world number one.
One more win would be enough for Pliskova to overtake Angelique Kerber, while Halep needs to win the title.
Pliskova said: "Coming into this tournament, there were a few people who told me: 'You have to be in the final to be number one'. I was like: 'There is no chance I (will) make the final here'.
"And now it's close, but it's close and it's far, because I'm playing against somebody who I would say is one of the best girls on clay.
"She's playing also for being world number one. So it's going to be a huge match."