The Russian seventh seed, who will take on Chinese sixth seed Li Na for a place in Saturday's final, needs only to lift the Suzanne Lenglen Cup to complete a career grand slam.
"It's really exciting to be back in the semis here, in general. I put a lot of work in to be in this stage of the grand slams," said Sharapova who made it to the last four at Roland Garros in 2007. "I'm really happy that it's here. I'm going to have a chance to go further."
Sharapova unleashed a devastating display of attacking tennis to leave her opponent flat-footed.
Petkovic did go 40-0 up in the first game but she was brought down to earth in ruthless fashion. Sharapova, who had not made it to a grand slam semi-final since the 2008 Australian Open, started to spray the court with forehand winners and sealed the opening set in 32 minutes.
Petkovic, who beat Sharapova in the Australian Open fourth round this year, took a bathroom break and came back fighting for her serve, but she dropped it in a 13-minute opening game.
The German finally stemmed the flow of Sharapova winners in the ninth game and broke to level at 2-2 as she mixed up her game with drop shots.
A trade of service breaks made it 3-3 but Sharapova raised her game again to push Petkovic far behind her baseline and the German eventually succumbed when she netted a routine forehand on the second match point. And so there was to be no Moon Walk for Bosnia-born Petkovic, who celebrates victories with Michael Jackson's famous backwards dance steps but, for Sharapova, the title is becoming a real possibility.
Petkovic said: "I think she played long. There were very strong balls, but she plays very long balls, as well, and you can't attack on her balls."
Sharapova, who four years ago described herself as a "cow on ice" on clay, has now improved on the slowest surface. She said: "There's no doubt that I've improved on this surface. There's no doubt that I felt, as the years went on, better and better."
Sharapova, who won the Rome tournament before arriving in Paris, is now on a ten-game winning streak on clay. She will face Li Na in the semi-finals after the Australian Open finalist put out title favourite Victoria Azarenka.
Li, who lost to Kim Clijsters in the final in Melbourne, was just too consistent for the fourth seed, winning 7-5, 6-2.
The other semi-final is between home hope Marion Bartoli and Italy's defending champion Francesca Schiavone.