The world No 1 was in control from the outset against a nervous-looking Australia's Ashleigh Barty, whose challenge was undone by a string of unforced errors.
The top seed, who claimed the Montreal title in 2016, won seven of the last eight games as she wrapped up a straightforward victory over the 22-year-old Australian in one hour and 11 minutes.
Spaniard Carolina Garcia, the No.6 seed, was combative in the first set before Halep secured a crucial break to win the opener 7-5.
Halep complained Friday about playing the first semifinal day after two straight night matches.
Ashleigh Barty of Australia drapes herself over the net after missing a return to Simona Halep
The Frenchwoman might have thought she was at a practice session with her team as she took on Maria Sharapova at the Rogers Cup third round, playing a feisty game with smooth, basic strategies to win over the Russian 6-3, 6-2.
She then raced through the second set 6-1 with minimum fuss.
"I think the match was a very good level of tennis even if the rhythm was a little bit mixed". "Simona Halep raises her game at just the right time", a commentator said anxiously. "Yeah, it's disappointing, but I think this will help me moving forward, getting ready to go into (Cincinnati) and the U.S. Open".
The world No.16 broke Berten's serve fours times and never faced a break point to book her first-ever semi-finals appearance in Canada. Sharapova had a lot of spunk and great rallies for her French opponent and she combined some good tactics, to lead in the first set 2-all but the Frenchwoman played a patient game and soon leveled the score to 3-all.
Barty, the world No. 16, has eclipsed her previous best at the tournament, a place in the last 16 when it was held in Toronto a year ago.
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The Egypt forward scored 44 times in his first season at Liverpool and took only 19 minutes to get off the mark at Anfield . On the trip to America, he scored penalties against City and United so that's another potential boost too.
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"We spoke also Petr did a very good pre-season, also today I think he played good also". We need two things: quality players, which we have, and then organisation.
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Ronaldo proved good value for the hype, scoring in the 10th minute with a neat finish after breaking a loose offside trap and closing in on goal completely unmarked.