Japanese chip maker Renesas Electronics Corp. said Tuesday it has agreed to buy California-based Intersil Corp. for about $3.2 billion, a step aimed at beefing up its strength as an automotive-related semiconductor provider.

Renesas will pay $22.50 a share for the U.S. chip maker, a premium of about 43.9% to the company’s Aug. 19 closing price, the last trading day before the company said it was in talks with Intersil. The deal is expected to be completed by the first half of 2017 after approval from Intersil shareholders...