In a match that lasted almost two and a half hours, fifth-seed Dementieva managed to overcome her compatriot Nadia Petrova (seeded 21) in three sets 6-1, 6-7 (6-8), 6-3.
"It feels wonderful. It's my first semifinal here and I'm very excited about it. It has been a good run for me. I'm happy I'm getting my game back," Dementieva said after the match, the WTA website reported.
In her semifinal match Dementieva is set to play defending champion Venus Williams. The American advanced to the semis by zipping past Thailand's Tamarine Tanasugarn in straight sets 6-4, 6-3.