The 19-year-old Russian, who is the only player to have won all her matches and not to have dropped a set, extended her winning streak to 19 matches with an emphatic 6-1 6-4 victory over fellow Russian Svetlana Kuznetsova.
She will now meet Justine Henin-Hardenne while holder Amelie Mauresmo takes on twice former champion Kim Clijsters in the other semi-final.
"I definitely think I'm a much better tennis player than I was a year or two ago but I think I can get even better and there are a lot of things to improve in my game," the US Open winner told reporters after her victory.
"I feel physically stronger, my muscles are building a bit and I feel as though I can play three-set matches and not worry about being fatigued afterwards.
"The US Open was a good example as I was able to take back-to-back wins over the number one and two players in the world. I couldn't have done that a year ago.
"I'm more experienced too and as you play more you feel like you know what to do in certain situations."
If Sharapova beats Henin-Hardenne and goes on to win the tournament she will take the prestigious year-end number one spot for the first time in her career.
World number two Maria Sharapova believes she is playing better tennis than at any time in the last two years after easing her way into the semi-finals of the season-ending WTA Championships on Friday.
The 19-year-old Russian, who is the only player to have won all her matches and not to have dropped a set, extended her winning streak to 19 matches with an emphatic 6-1 6-4 victory over fellow Russian Svetlana Kuznetsova.
She will now meet Justine Henin-Hardenne while holder Amelie Mauresmo takes on twice former champion Kim Clijsters in the other semi-final.
"I definitely think I'm a much better tennis player than I was a year or two ago but I think I can get even better and there are a lot of things to improve in my game," the US Open winner told reporters after her victory.
"I feel physically stronger, my muscles are building a bit and I feel as though I can play three-set matches and not worry about being fatigued afterwards.
"The US Open was a good example as I was able to take back-to-back wins over the number one and two players in the world. I couldn't have done that a year ago.
"I'm more experienced too and as you play more you feel like you know what to do in certain situations."
If Sharapova beats Henin-Hardenne and goes on to win the tournament she will take the prestigious year-end number one spot for the first time in her career.
