Filip Chlapik gave Czechia a 5-3 lead 1:05 into the third period, scoring after Necas' shot bounced off Neckar and went behind him, where Chlapik put it in.
Roman Cervenka, the Czechia captain, made it 6-3, scoring with a backhand on a breakaway at 1:53. Neckar was replaced by Junca after the goal.
"Obviously we were not happy with the way we played in the first," Bellemare said. "Bunch of passes that we were trying; that's not the way we can play with those guys. Too much talent. … At that level, with that type of talent on the other side, you make those mistakes, you're going to pay the price."
Boudon scored on a rebound on the power play at 1:01 of the second period to pull France within 2-1. He then tied the game 2-2 at 4:04, scoring on a 2-on-1 set up by a turnover he created in the defensive zone.
Hugo Gallet made it 3-2 at 5:54, scoring 1:50 after France had tied it.
"I think that's the moment which [is] going to stay in my mind all my life long," Neckar said. "When Gallet scored his goal, and we were [up] 3-2, I was really thinking, 'Is the dream going to really happen?' At the end of the of the day, no, but I'm really happy how we battle.”
Necas gave Czechia a 1-0 lead with a power-play goal at 5:56 of the first. He took a cross-ice pass from Pastrnak and one-timed the puck past Neckar.
Kempny increased the lead to 2-0 at 13:04 with a slap shot from inside the blue line.
Each team concludes group play Sunday, with Czechia playing Switzerland (6:10 a.m. ET; Peacock, CNBC, ICI TOU.TV, CBC Gem, SN, RDS) and France facing Canada (10:40 a.m. ET; Peacock, USA, ICI Télé, CBC Gem, RDS2, CBC).
"We're just trying to get better every game," Necas said. "It's a short tournament. Hopefully we get good rest tomorrow and the game against the Swiss."