"This court is special for me and I was trying to enjoy every point", Kerber said of Rod Laver Arena, where she beat Serena Williams in the 2016 final.
"For sure it wasn't my best start but I knew I had to restart after 3 games to stop missing and move better", said Halep, whose relentless chasing and powerful groundstrokes overwhelmed her taller, tattooed opponent.
"In the first set it was very close so I knew I needed to step up", said Pliskova, who reached her second last eight at the Australian Open.
Halep, still looking for her first Grand Slam title, was under the cosh in the opening stages of the match as 72nd-ranked broke the Romanian for a 3-2 lead.
But she has been nursing a painful ankle and an aching body after enduring a 3 hr 44 min thriller to beat Lauren Davis 15-13 in the third set in round three.
Simona Halep's ankle seemed to give her no trouble in her win over Naomi Osaka.
The top seed dominated the Czech completely and took just about an hour and 11 minutes to win 6-3, 6-2 and reach her maiden senior semi-final at the Melbourne Park. "I served well so everything went pretty well for me".
The American never settled into the match - much like her US Open final appearance, when she was similarly crushed by Sloane Stephens - with her poor record against Kerber perhaps in her mind.
The 26-year-old Romanian world number one, still without a grand slam title, trailed 3-0 but battened down the hatches to reel off the next nine games on her way to a first Melbourne semi-final.
She took nearly three hours to get past fellow Czech Barbora Strycova in a last-16 match that did not finish until just before 2:00 am on Tuesday.
"I think it will be a long match with a lot of long rallies", Kerber said.
This is set to be an intriguing match, but with possibly fitness issues and the amount of time Halep has already spent on court, the world No.1 will be sent packing. "I'm just happy to get through and to be again in the semis here".
"I was just trying to play my game", Pliskova said.
For a while it appeared former Australian and U.S. Open champion Kerber's progression could unravel against No. 88 Hsieh Su-wei, a former top-ranked doubles player with a double-handed grip on both sides, until she regained momentum for a 4-6, 7-5, 6-1 win.