It's the first berth in a major final for the 22-year-old Safina. Her brother, Marat Safin, is a former No. 1 player who won the 2000 U.S. Open and 2005 Australian Open.
"I'm doing it for him and for myself," Safina said.
Her opponent Saturday will be the winner of the second semifinal, an all-Serb affair between No. 2-seeded Ana Ivanovic and No. 3 Jelena Jankovic.
Safina, seeded 13th, was one point from defeat against top-ranked Maria Sharapova in the fourth round and No. 7-seeded Elena Dementieva in the quarterfinals before mounting comebacks.
But against the error-prone Kuznetsova, Safina took a 4-1 lead and cruised the rest of the way.
"I won in two sets - that's strange for me," Safina said. "Once I had a set, then I knew I can push a little bit more. Then fire comes and you really like start to fly."
Kuznetsova, the 2004 U.S. Open champion, hardly looked like a No. 4-seeded player as she struggled to keep her groundstrokes in the court. She said she was tight and unable to get comfortable because Safina's penetrating shots pinned her well behind the baseline.
"It was pretty horrible," Kuznetsova said. "I felt pretty bad out there. I felt like I could not give her fight because I was fighting first against myself."
By the second set Kuznetsova became so frustrated that after yet another errant shot, she angrily smacked a ball into the 12th row at the far end of the stadium.
The outburst failed to help. Safina broke in that game for a 3-2 lead and overcame two break points to win the next game. Soon she was serving for the match, and one final shanked forehand by Kuznetsova gave Safina the victory.
Her best previous Grand Slam showings were quarterfinal finishes in 2006 at Roland Garros and the U.S. Open.
"It feels amazing," Safina said. "I didn't expect that I could get to the final. I think the less you think, the better it is. Because when you less expect it, the result comes."
Safina said her brother, who lost in the second round, is in England preparing for Wimbledon.
"He won't show up for the final," she said. "If it's going to be live (on TV), I guess he will watch it."
She'll try to become the first woman to win a Grand Slam title after saving match point in two matches.
The men's semifinals Friday will include the world's three top-ranked players - No. 1 Roger Federer, No. 2 Rafael Nadal and No. 3 Novak Djokovic - and Frenchman Gael Monfils, at No. 59 the lowest-ranked men's semifinalist at Roland Garros since 1999.
Monfils plays Federer, who is seeking the only Grand Slam title he has yet to win. Djokovic faces Nadal, who is 26-0 at Roland Garros and two wins from a fourth consecutive French Open title.
