Williams, a 13-time Grand Slam champion, needed just 59 minutes on Saturday to subdue the big-hitting German and reach her first final since she won Wimbledon in 2010.
That victory was followed by an 11-month absence from the court as she coped with a series of health problems, including a cut foot and blood clots in her lungs.
“I feel like a kid again,” said Williams, whose ranking has dropped to 169. “When I was younger I had the goal of being in the top 100, then qualifying for a Grand Slam without a wild card. I have those goals again.”
Williams reached the second round on her return at Eastbourne and reached the fourth round at Wimbledon.
In Sunday’s final she’ll face France’s Marion Bartoli, who ended her title defence at the All England Club.
Bartoli advanced on a walkover after eighth-seeded Slovakian Dominika Cibulkova withdrew with a strained abdominal muscle.
“She should be fresh and I will be ready,” Williams said. “It’s a whole new match and I’m a better player than I was at Wimbledon. This is great progress and I’m excited about my potential as I go forward.”
Williams had booked her semi-final date with Lisicki with a quarter-final victory over Maria Sharapova.
Lisicki had never played Williams before, and admitted it took her a while to adjust to the American’s power.
“I did not know what to expect,” Lisicki said. “I’m not used to having the ball come back at me so hard. It was a new experience, a learning experience.”
Williams was pleased that she was able to make use of her power without too many errors.
“I want to make fewer mistakes,” Williams said. “I was trying to go for the shots when it’s right.”
Bartoli, ranked ninth in the world, reached her fourth final of the year and her third at Stanford, where she won the title in 2009.
The Frenchwoman had reached the semis after playing just one set of her scheduled quarter-final against Ayumi Morita, before the Japanese withdrew trailing 6-1 due to the ankle injury.
“This has never happened to me but there’s not much I can do about it,” Bartoli said. “It’s a shame Dominika had to be put out. It will be an extremely tough match tomorrow and I need to get ready.”
Cibulkova said she had been troubled by the injury all week.
“It was painful when I played Marina (Erakovic), but I was able to get through that match,” she said.
“I thought it would be better in the morning, but I saw a doctor and he recommended not playing since the injury could worsen.”
Cibulkova missed two tournaments with an abdominal strain after reaching the quarter-finals in Madrid.
“Maybe I rushed to play too quick,” she said. “I don’t want to make the same mistake.”
Cibulkova said she would make the trip down the coast to San Diego, where she is scheduled to play on Wednesday.
“It’s still open and I’m hoping to be ready,” she said.