Eder Militao's own goal at the Bernabeu had Barca heading into Thursday's (AEST) second leg with a 1-0 advantage, but Vinicius' goal in first-half added time got Madrid back into the tie.

Carlo Ancelotti's men then took over after the break, Benzema putting them ahead with a sublime finish before coolly converting from the spot after Vinicius was felled.

The reigning Ballon d'Or winner clinched his hat-trick late on to dump the 31-time winner out and set Madrid up to meet Osasuna in the showpiece match on 7 May.

Barca started brightly with Sergi Roberto and Raphinha seeing early efforts foiled, though alert defending was needed by Ronald Araujo at the other end to deny Vinicius.

Tempers were starting to fray in a typically high-charged encounter, Xavi booked for dissent before Gavi and Vinicius were cautioned for a fracas in midfield. The visitors remained focused, though, to level the tie just before half-time.

After Courtois made a superb stop to deny Robert Lewandowski, Madrid flew up the other end, and though Jules Kounde initially blocked Vinicius' shot, it crept over the line to make it 1-1 on aggregate.

Ancelotti's side took the lead shortly after the break, Luka Modric teeing up Benzema to expertly stroke into the bottom-left corner.

Madrid then landed a killer blow shortly after, Franck Kessie bringing Vinicius down in the box for a penalty before Benzema stepped up and ruthlessly slotted into the bottom-right corner.

Benzema sealed his hat-trick with 10 minutes to play, delicately dinking over Marc-Andre ter Stegen to send his team cruising into the final.