The two sides went into the game looking to earn a final berth but it was the hosts who did so after a tight game at a bouncing Estadio Ramon Sanchez Pizuan.
With the game finely poised following the 1-1 draw in the first leg, Leganes started well, with Claudio Beauvue flicking an effort over at the near post after good work from Nabil El Zhar.
However, with just 15 minutes gone, the hosts took the lead. Luis Muriel drifted into the channel down the right and when his first attempt to cross form the byline was blocked, he was the first to react to square for Joaquin Correa to tap into an unguarded net from six yards.
Despite the blow, Leganes reacted admirably, with Gabriel Pires seeing a low effort easily gathered by by Sergio Rico, before Beauvue flicked a header just over.
After a first half of few chances, Sevilla twice went agonisingly close to extending the lead on the stroke of half-time.
First, Muriel once against drifted into the channels, beating his man down the left before cutting the ball back for Ever Banega, only for the midfielder’s low effort to be scrambled off the line by the retreating Tito.
Tito was then called into action just minutes later as he hacked and effort from Sergio Escudero off the line after the centre-back rose highest to meet a corner from the right at the back post.
The defender's intervention meant that Sevilla went in at the break with just a one-goal lead.
Leganes continued to put up a spirited fight in the second period, with Beauvue seeing a curling free-kick narrowly clear the bar before Ruben Perez's powerful drive drifted just wide of Rico’s right-hand post.
As the game passed the hour mark, Sevilla wasted two golden chances to seal the win.
Muriel was sent racing clear but a poor first touch allowed Dimitris Siovas to get back and make a challenge, before Pablo Sarabia could only fire straight at Nereo Champagne when well placed.
As the minutes ticked away Leganes started to throw men forward in search of the goal that they craved, but that goal never came and instead it was Sevilla who scored the game’s all-important second.
After thwarting a Legnaes attack, the hosts countered. Substitute Sandro Ramirez fed Vazquez and he beat his man on the outside before rifling the ball past Champagne and into the top corner at the near post.
Sevilla can now look forward to a final against either Barcelona or Valencia, with the duo set to face off on Thursday in the other semi-final.
7 February 2018
For Leganes their dreams of a shock final appearance are over, but a historic cup run that saw them beat Real Madrid for the first time in their history will never be forgotten.