Klizan needed just 64 minutes to beat the second-seeded German veteran, who was clearly struggling with the right shoulder injury that had kept him out of action since March 13, when he lost to Roger Federer in the fourth round at Indian Wells.
"It wasn't a great match for the fans because Haas couldn't play like that. Now I'm looking forward to the final," the 111th-ranked Klizan said.
Fognini needed just over an hour to ease past German qualifier Jan-Lennard Struff 6-3, 6-1 in the other semifinal.
"It was a difficult match," Fognini told the ATP website. "I am happy because I am in the final on my debut here."
Fognini beat Klizan in their last three meetings but the Slovakian defeated the 15th-ranked Italian in his only previous ATP World Tour final, at St. Petersburg in October 2012.