It is the first time the 19-year-old has won three matches in a row since her run to the US Open title in 2021.
The British number one is yet to drop a set at the WTA tournament.
She will face top seed Jelena Ostapenko, who beat teenager Victoria Jimenez Kasintseva 6-2 6-1, in order to reach the final.
Raducanu made a strong start, racing into a commanding 4-0 lead, and not dropping a point on her first serve as she easily won the opening set.
However, Poland's Linette had three break points on Raducanu's first service game in the second set.
But the former world number 10 reasserted herself, winning five points in a row to hold serve before breaking Linette for a 2-1 lead.
Linette had to take a medical off-court timeout, with Raducanu using the break to practice her serve, and the Briton continued to dominate to establish a 5-1 lead.
Raducanu then served out the match with ease, claiming victory in one hour 16 minutes and leaving the court with a smile and thumbs-up for the fans.
British number two Dan Evans won through to the quarter-finals of the San Diego Open with a 6-4 6-4 win over Japan's Taro Daniel. He will play Constant Lestienne from France on Friday.