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Playing in his second ATP Tour-level semi-final of the year, 19-year-old Fonseca hammered down eight aces and struck 39 winners during the contest.

The opening set was closely contested, with little to separate the pair before Fonseca edged ahead in the tiebreak, clinching a 4-3 lead and eventually taking the set.

Munar, 28, began the second set brightly, racing to a 4-2 advantage, but Fonseca showed resilience to level the score at 4-4. The youngster then claimed three of the next four games to seal the victory and advance to the final.

Fonseca, who is chasing his second ATP Tour title after lifting his maiden trophy in Buenos Aires in February, could break into the world top 30 for the first time if he defeats Davidovich Fokina in the final.

"It's been an amazing year, starting at number 130 in the world, now 40-something and into a first ATP 500 final," Fonseca, who is the world No.46, said.

"We didn't go to Asia this year, I was a little bit sick. I was working with my mentality and I'm getting the opportunities ... I'm just very happy to be here.

"I knew that it was going to be a tough match, Jaume is playing [well] on this surface. He's putting a lot of pressure and you need to defend a lot of the time.

"I don't like playing against those guys because I like to play aggressive and go for winners.

"I'm happy with how I stayed mentally after an early break in the second set. I'm very happy, so let's stay hyped for the final."

In the second semi-final, Spain's Davidovich Fokina advanced to his fourth final of the season after Frenchman Ugo Humbert retired while trailing 7-6 (7-4) 3-1.