The world No.1 follows Novak Djokovic, Rafael Nadal and Roger Federer in completing the set and, at 24, has done so at a younger age than his illustrious predecessors – taking a year off Djokovic's previous record.
The Italian will face a familiar foe on Sunday after second seed Alexander Zverev defeated Alexander Blockx 6-2 7-5 in the other semi-final.
Sinner has been open about finding the conditions at the Caja Magica difficult but he has dropped just one set this fortnight and was mightily impressive against one of the tour's most in-form players in Frenchman Fils.
The top seed did not face a break point throughout his 6-2 6-4 victory and is now only one victory away from becoming the first man to win five successive Masters titles.
Chasing his second clay-court title of the season, the Italian controlled the baseline exchanges and mixed in deft drop shots to hand Fils his first defeat on the surface this year.
The Frenchman offered more resistance in the second set, varying his play to stay in touch, but Sinner secured the decisive break before closing out the match in 85 minutes.
"Obviously very, very happy," said Sinner. "One more final here, it's an amazing result.
"For me, the most important was trying to raise my level today, which I've done, especially first set – very, very aggressive and I'm changing direction very well. I'm very happy to close it out in two and it means a lot to me, of course."
Sinner has not been beaten since a surprise loss to Jakub Mensik in Doha in February, winning titles in Indian Wells, Miami and Monte Carlo, with his unbeaten streak now at 22 matches.
Three of those have been Masters semi-finals against Zverev who will be seeking to end a miserable run of eight straight losses against Sinner.
The German prevailed in four of their first five contests but has not won a set in their last five meetings.
Zverev, the 2018 and 2021 champion, wrapped up his victory in just over an hour and a half to reach his fourth final in Madrid.
He breezed through the first set but the second was more of a slog as he spurned seven break point opportunities, finally doing so at the eighth attempt following a fortunate net cord to the chagrin of his unseeded Belgian opponent.
with Reuters
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