The defending champion overcame 11 double-faults and won a shriekfest against Victoria Azarenka in the semifinals Thursday, 6-1, 2-6, 6-4.
Sharapova's opponent Saturday will be the winner of the semifinal between No. 1 Serena Williams and Sara Errani. Sharapova beat Errani in the final last year to complete a career Grand Slam.
"This is such a special tournament for me, obviously being the defending champion," Sharapova told the crowd. "It was really my goal to get to the final stage."
She advanced past Azarenka with a clamor. The two most notorious grunters in tennis wailed on nearly every swing, matching pitch and volume as they swapped powerful shots from the baseline. They sounded as if they were pushing a stalled Peugeot across lanes of traffic in the Arc de Triomphe.
"Come on, Monica," a spectator yelled at Sharapova, referring to one of the game's great grunters, Monica Seles.
The aggressive swings resulted in a seesaw semifinal. Sharapova whacked 12 aces but was erratic with her second serve, and her groundstrokes were also unpredictable.
She needed five match points to seal the victory. Serving for the victory for the second time, she held at love and finished with an ace.
"Those last few points are the toughest," Sharapova said. I'm so happy that I regrouped and came out at 5-4 and served it out really well."
Following a 35-minute rain delay before the third set, Sharapova hit four double-faults in a single game, the last of them on break point, to make it 2-all. She struggled again with her serve at 5-2, losing a tense, sloppy 12-minute game when she squandered four match points and double-faulted on the final two points.
She was steadier at the end, however, and after accepting a cursory congratulatory handshake from Azarenka, Sharapova screamed through a grin.
She improved her record at Roland Garros to 43-9, best among active women. That includes victories in her past 13 French Open matches.
Azarenka, a two-time Australian Open champion, was playing in her first Roland Garros semifinal. She still believes she can win a clay-court Grand Slam title.
"Oh, sure," she said. "Not this year."
In the men's semifinals Friday, seven-time champion Rafael Nadal plays No. 1 Novak Djokovic for the 35th time, and Frenchman Jo-Wilfried Tsonga faces Spaniard David Ferrer.
Sharapova, who lost her opening set in the quarterfinals 6-0, started slowly again against Azarenka. Sharapova double-faulted twice in the first game and was broken at love.
But this time she quickly righted herself, temporarily finding the range with her serve and cracking ferocious returns. She won 22 of the final 26 points in the first set and closed it out with an ace.
"The serve is definitely something that you never know what to expect," Azarenka said.
Then Sharapova began to misfire while Azarenka found her timing. Consistently stepping into the court and smacking groundstrokes close to the baseline, Azarenka swept the final four games of the second set to even the match.
Next came rain, and when the match resumed both players struggled to find any rhythm. The tennis was louder than the crowd in the third set when subdued fans quietly endured a flurry of errors forced and unforced by the two big hitters.