semifinal match; semifinal game
Refers specifically to a match or game in the semifinal round of a tournament. Often used in sports contexts.
The semifinal match will be held tomorrow.
He lost in the semifinal game.
準決勝 refers to the semifinal round itself, while 準決勝戦 specifically refers to a match or game within that round.
決勝戦 is the final match, whereas 準決勝戦 is the semifinal match.
quarterfinal match
Compound of 準 (jun, 'semi-') + 決勝 (kesshō, 'final round') + 戦 (sen, 'match').