SAN FRANCISCO — Patent litigator Steven Carlson is leaving Fish & Richardson to lead the Silicon Valley office of Kasowitz.

Carlson, who fields disputes involving patents and trade secrets, arrives as Kasowitz Benson Torres & Friedman rebuilds in the Valley. Last week, the head of the less than two-year-old office, Douglas Lumish, jumped to Latham & Watkins with two other Silicon Valley-based partners and a New York-based partner. Two associates in the Valley have followed the team to Latham so far.