The second-seeded Sharapova defeated Maria Kirilenko 3-6, 7-5, 6-2 and will face former champion Ana Ivanovic with a berth in the title match on the line.
Sharapova found herself at deuce while serving at 4-4 in the second set, and a loss in that game would have given Kirilenko a chance to serve for the match. Sharapova held serve, however, and went on to fight off the upset bid.
Ivanovic pulled off a surprise when she defeated seventh-seeded Marion Bartoli 6-3, 6-4 in the quarterfinals. Thursday's win followed a victory over former world No. 1 Caroline Wozniacki in the fourth round Tuesday.
The other semifinal, which was determined Wednesday, will send current world No. 1 Victoria Azarenka against Angelique Kerber.
Azarenka has won all 21 matches in which she has competed this year. She defeated Sharapova in the championship match of the Australian Open in January.
Wisconsin business offering 'therapeutic cuddling' forced to close
Costly malfunction causes beer flood at Boston-area brewery