Egyptian world number 12 Momen outlasted his German opponent in a gruelling 77-minute encounter, coming through 7-11 11-4 7-11 11-7 11-8.
Momen's appearance in the last four will mark the first time he has reached that stage of the a PSA World Squash Series event.
And the task could not be more daunting for the 26-year-old, who is poised to take on world number one Gregory Gaultier after the Frenchman comfortably dispatched England's Daryl Selby 11-2 11-3 11-8.
However, Momen is not fazed by the challenge facing him and insists all the pressure will be on Gaultier.
"It was a huge battle against Simon," Momen said.
"I didn't think about being in the quarter-finals with the prospect of making my first World Series semi-finals - I just wanted to take it point-by-point and the level of play from both of us just kept getting better and better.
"It was a nice match to play in and I'm really happy to win.
"I'm really excited about being in the semi-finals now. I've been on tour for eight years and even at this point to experience something new like that is very exciting.
"Greg is the number one and the one positive to take from that is that there is no pressure on me. We played here in the quarter-finals last year and I played well then and I just want to enjoy myself on court, enjoy being in the semi-final and play my best."
Second seed Mohamed Elshorbagy kept the prospect of an all-Egyptian final intact by coming from a game down to defeat England's Peter Barker 9-11 11-7 11-9 11-3.
Elshorbagy will meet Spaniard Borja Golan in the other semi-final after last year's runner-up overcame Nicolas Mueller of Switzerland 11-7 11-9 11-7.