"It was very tough and very hot," Haase said. "He was the better player in the first set. I didn't have a chance. From the end of the second set, I managed to put him under some pressure."
The Dutchman will play eighth-seeded Marcel Granollers of Spain. Juan Monaco of Argentina takes on Albert Montanes of Spain in the other semifinal.
After winning in 2011 and '12, Haase is now 12-0 at the event. He beat Granollers on a third-set tiebreaker in the quarterfinals in Gstaad a week ago. Granollers had five aces and held serve throughout to beat Leonardo Mayer of Argentina 6-3, 6-1 and reach his first semifinal of the season.
The second-seeded Monaco advanced to his third semifinal of the year by defeating Daniel Gimeno-Traver of Spain 6-2, 3-6, 6-4. The Spaniard had beaten Monaco from two sets down at Roland Garros in May, but couldn't complete a comeback this time.
Montanes defeated Dominic Thiem 6-4, 6-3 in the 19-year-old Austrian's first career quarterfinal.