Google Inc. accused its former driverless-car executive Anthony Levandowski of quietly developing a competing company for more than three years before he left the internet giant and eventually sold the business to Uber Technologies Inc., according to legal documents released Monday.

Mr. Levandowski earned more than $120 million at Alphabet’s Google “for his supposed contributions” to develop the company’s self-driving car program, now called Waymo, according to a Google suit against Mr. Levandowski included in the documents.

The court filings offer new details about an alleged scheme by Mr. Levandowski and other former Google employees to steal technology that is at the center of a seven-week-old battle between Uber and Waymo in U.S. District Court in San Francisco.

Neither Mr. Levandowski nor his lawyers responded to requests for comment.

Waymo sued Uber in February for allegedly stealing trade secrets to jumpstart its own self-driving-car program last year. Uber is fighting the lawsuit and has argued in legal documents that many of the claims should be instead brought against Mr. Levandowski in employment-arbitration proceedings.