In 1991 the FA decided that only one replay should be played (starting with the 1991--92 competition). If this game ended in a draw, extra time would be played, followed by penalty kicks if the match was still even. In 1999 it was decided that the semi-finals should be decided in one game, with extra time and penalties used to determine the outcome if the game ended in a draw. Replays are still used in earlier rounds, however, though were eliminated in the quarter-finals in 2016. The last FA Cup Semi-final replay, in 1999, saw Manchester United take on Arsenal at Villa Park. This turned out to become one of the most memorable semi-finals of all time, with Peter Schmeichel saving a last-minute penalty from Dennis Bergkamp and a Ryan Giggs extra time goal deciding the outcome in Manchester United's favour. In 2003 this goal was voted the greatest ever in FA Cup history.

What's the best answer to this question: is there extra time in fa cup semi final?
yes