Semel had served as non-executive chairman at Yahoo after being replaced as chief executive last summer by co-founder Jerry Yang. Yahoo said earlier this week that it plans to lay off 1,000 workers after reporting fourth-quarter earnings down significantly from a year ago.
The company said in a statement Thursday that Semel had begun discussions several months earlier about leaving the board in January. Roy Bostock, who has served on the Yahoo board since 2003, will replace Semel as chairman. Separately, the TechCrunch blog was reporting Thursday that Yahoo had acquired broadband video company Maven Networks for about $150 million. The deal is expected to be announced today.
--Mark Walsh