Garcia has been tipped as a potential Grand Slam victor since she burst into the limelight in 2011 as a wild card and led former world number one Maria Sharapova 6-3 4-1 in the second round.
Halep went from out-of-sorts to on-target against Kerber, scrambling to every ball and staying the course to erase an early deficit.
'And I think we played many matches.
In her 31st non-consecutive week as the world No.1, Halep will face Garbine Muguruza to defend the top spot in the semifinals.
Sharapova, back at the claycourt slam for the first time since 2015 following a doping-ban, walked on court with two French Open crowns to Muguruza's one and a 3-0 head-to-head record against the reigning Wimbledon champion.
The victor of Thursday's semi-final will also decide the world number one spot which Muguruza held for four weeks previous year.
"She did a lot of things better than I did", Sharapova said in a press conference after the match.
However, this is usually the point in grand slams where Halep falls apart, so it's going to be interesting if the Romanian can finally close the deal on the big stage and put herself in elite company.
An anti-climactic match ended predictably, with a Sharapova backhand nestling in the net - her 27th unforced error.
"To have had the victories that I have had, to have the results that I have, obviously moving a step in the right direction", said Sharapova who had made the last-eight in Madrid and semis in Rome in the run-up to Paris.
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How do the Cavaliers bounce back from that, especially after absorbing an even more painful setback in Game 1 last Thursday? Durant is incredible, but his isolation sets have had a tendency to drag down Golden State's offense at times.
Sharapova's eagerly-awaited fourth-round clash with Serena Williams never even made it on court on Monday as her American nemesis pulled out an hour before the scheduled start with a pectoral injury.
Though Kerber, sensing a pendulum swing, cut her passive play out and began to construct her most aggressive points of the match, Halep would be able to protect that advantage throughout the set.
But the 26-year-old amassed six of her 30 unforced errors in the first in the tiebreaker.
In the other men's quarter-final, number three Marin Cilic and number five Juan Martin del Potro were at 5-all in a first-set tie breaker when the match-up of past US Open champions was stopped.
Spain's Garbine Muguruza thrashed Maria Sharapova to reach the French Open semi-finals on Wednesday as a second top-of-the-bill showdown in three days failed to materialse at Roland Garros.
"Before, I gave it a lot of importance so that's why you're fighting every week, and I got there".
"But it's also not being dumb", she said with a laugh. The last time the two were scheduled to play was in Qatar in February, but Halep was forced to retire.
It ranked among one of the most lopsided losses ever suffered by Sharapova in her Grand Slam career.
Angelique Kerber appeared on her way toward an easy win like Muguruza, going up 4-0 in the first set.
It wasn't an easy win till Kerber needed a medical timeout in the third set.