|Belinda Bencic of Switzerland serves the ball to Simona Halep of Romania during the WTA Dubai Championships. (KARIM SAHIB/AFP) |
Bencic, ranked 56, followed up her third-round knockout of number eight Aryna Sabalenka, where she saved six match points, with her two-and-a-quarter hour win over 2015 champion Halep.
Former world number seven Bencic will next play two-time champion Elina Svitolina, who defeated Carla Suarez Navarro 6-2, 6-3, for a place in the final.
"I fought and stayed in the match. I'm happy I didn't give up. I didn't give her any free points. I was still there," said Swiss star Bencic whose career has been blighted by a series of back and wrist injuries.
"I'm just really happy that I'm back. I knew it was still in me, even after the injuries. I had to work my way back, I'm happy that I could finally show it."
Bencic broke the Halep serve seven times while losing her own on five occasions.
Bencic profited from a break for a 5-2 lead in the final set but needed three chances a game later to close out victory as Halep drove a forehand long.
Halep, the losing finalist last week in Doha to Elise Mertens, said she was feeling tired throughout.
"I was tired. After the second set, I felt like I'm getting cramping a little bit. It's normal. I was sweating a lot.
"She played very well and in the end, was a little bit stronger."
The Romanian added that she started to feel her Achilles tendon, which affected her serve.
'SCREAMING LIKE A BABY'
"I felt it the last match a little bit. But there are no excuses, just the fact that I'm tired."
Meanwhile, Hsieh Su-wei won the last six games to beat fourth seed Karolina Pliskova 6-4, 1-6, 7-5 and will next face a woman she has never beaten - two-time Wimbledon champion Petra Kvitova.
Second seed Kvitova, winner of the Dubai event in 2013, crushed Viktoria Kuzmova of Slovakia 6-4, 6-0.
Kvitova has won all four of her meetings with Taiwan's Hsieh, most recently in the second round of January's Sydney International.
Pliskova had looked in command in Thursday's final set, serving at 5-1 and then 5-3.
The persistent Hsieh kept up the pressure, narrowing the gap and levelling with a second straight break at 5-all.
Hsieh then held for 6-5 and clinched the upset a game later on a second match point after two hours.
"I was screaming like a baby when I won," 31st-ranked Hsieh said. "It was a tough comeback."
"She had a lot of aces (nine), I'm just happy I was able to make it back."
Pliskova had reached at least the semi-final at her previous three Tour events, dating to the Singapore ATP Finals in October.
"I was obviously tired today, my legs were not doing much. It was a tough match. To play against her, you need to be ready on the legs a lot, which I was not," said the Czech.
Kvitova, winner of the event in 2013, beat Kuzmova in just 62 minutes and said she felt her game was on the rise again after losing the Australian Open final to Naomi Osaka and winning just one match a week later.
"Today was the first day of the better days on court, off the court. It's been tough since I came from Australia and St. Petersburg.
"I'm glad that it's on the way up."
Elina Svitolina (UKR) bt Carla Suarez Navarro (ESP) 6-2, 6-3
Hsieh Su-Wei (TPE) bt Karolina Pliskova (CZE) 6-4, 1-6, 7-5
Petra Kvitova (CZE) bt Viktoria Kuzmova (SVK) 6-4, 6-0
Belinda Bencic (SUI) bt Simona Halep (ROM) 4-6, 6-4, 6-2