Haas, who dumped out world No.1 Novak Djokovic earlier this week, looked set to claim another famous scalp when he took the first set.
Ferrer came storming back, though, to level matters and although the Spaniard trailed 3-1 in the decider, he showed his typical resolve to seal a 4-6, 6-2, 6-3 triumph and set up a clash with either Andy Murray or Richard Gasquet – who played late last night – in tomorrow’s showpiece encounter.
Haas came flying out of the traps, winning four games in a row to open up a 5-2 lead, but Ferrer lived up to his reputation of fighting for every point and clawed one of the breaks back but Haas held his nerve..
The world No.5 had clearly taken some heart from his belated fightback and was formidable on serve in the second set. He did not concede a single break point and levelled 6-2. In the third set the never-say-die Ferrer stormed back to take the next four games before sealing victory.
Laura Robson and Lisa Raymond continued their stunning run in Miami by thrashing world No.1 pair Sara Errani and Roberta Vinci 6-1, 6-2 to reach the final.