The Germans beat Argentina 4-3 in a penalty shootout following a 3-3 draw on Tuesday. France defeated Mali 2-1.
Paris Brunner scored two goals for France and Max Moerstedt added the other in Surakarta.
Argentina forward Agustine Roberto scored a hat trick for his team, taking his tally to eight goals at the 24-nation tournament.
Yvann Titi and Ismail Bouneb scored a goal each for France, which won the U17 title in 2001. Ibrahim Diarra scored for Mali.
Saturday's final will be played in Surakarta. Argentina and Mali will meet in the same city a day earlier in the playoff for third place.
AP