The Italian won his 22nd straight match to book a place in Sunday's final, where he will aim to win a record fifth consecutive Masters 1000 title.
With his chief rival Carlos Alcaraz out injured, Sinner is the firm favourite to triumph at the Caja Magica and add to recent titles at Indian Wells, Miami and Monte Carlo.
The 24-year-old will face second seed Alexander Zverev or promising Belgian Alexander Blockx in the final.
"I played at a very high level, but I focus on always raising my level a little. Especially when the tournament gets serious... You have to raise your level if you want to keep going," Sinner told Movistar.
The Italian admitted he was feeling a little tired after playing so many matches of late.
"Obviously, there's a bit of fatigue - mentally I feel good, but there is some physical tiredness, my body isn't completely fresh, but that's normal, and I think it's a very positive thing for me, because it means I'm playing a lot of matches," Sinner said.
"Of course, on Sunday we'll try to do even better, but whatever happens, I've reached another final in a very important tournament."
Beating Sinner right now seems a near-impossible feat, and the four-time Grand Slam winner started superbly against Barcelona Open winner Fils, who has impressed since returning from injury in February.
The Italian broke in the third game when Fils went long to lead 2-1.
Sinner broke again in the fifth game with Fils, ranked 25th in the world, unable to cope with his sheer power.
The Frenchman has not yet reached a Masters 1000 final, and with Sinner in sumptuous form, it quickly became clear he would have to wait a little longer.
Sinner wrapped up the first set on his serve after Fils found some fighting spirit to prevent a third break.
The second set was far closer, with Fils rising in confidence and belief.
The 21-year-old saved two break points for a 3-2 lead, and put pressure on Sinner's next serve, although the Italian produced two aces to hold.
Sinner broke with a down-the-line backhand winner to end an excellent rally for a 5-4 lead and served it out to triumph.
