The 27-year-old beat Williams 6-0 in just 103 minutes with breaks of 43, 46, 70, 122, 51 and 73.

He will now take on defending champion John Higgins for a place in the final.

The win was especially sweet for Lee as Williams had beaten him in the three previous years in Glasgow.

"I'm over the moon with that because Mark usually plays out of his skin against me," said the world number seven.

"Normally I just sit there and watch so I would have settled for 6-3, 6-4 or even 6-5.

"But I was just trying to do a job on him today. I thought if he wants to go for the long pots let him but don't leave him any easy ones."

Lee put the manner of the victory down to a new self-belief that had been missing until last season.

Williams was despondent after the defeat.

"You try hard in every tournament but I never seem to do well here. Stephen is playing well but I made it too easy for him," he said.

Stephen Hendry gained revenge over Peter Ebdon for his defeat in the final of the Embassy world championships with a 6-4 victory in their quarter-final.

The match rarely reached the heights of the pair's 18-17 thriller at The Crucible but it did include a 136 total clearance for Hendry in frame six.

Hendry will face Ronnie O'Sullivan in the other semi-final on Saturday night.

"It was a poor standard. I felt good in the first couple of frames but after that the balls seemed to run awkwardly for me," said Hendry.

"However, you've got to win these matches when you are not playing well just like those when the centuries are flying in.

"I will certainly have to improve my standard to beat Ronnie, though it's likely to be a much faster game."