The International Trade Commission is investigating a complaint that Sanyo Electric Co. of Japan and two Taiwanese companies, Winbond Electronics Corp. and Macronix International Co., violated patents held by Atmel Corp. of San Jose. In a complaint filed last month, Atmel accused the three companies of selling semiconductor products that are similar to products patented by Atmel. Atmel said it suspected the alleged violations late last year when the company noticed "considerable erosion" in prices, Atmel attorney Valerie Menager said. Macronix President Alan Portnoy said the company is "absolutely not" copying Atmel's material. Sanyo and Winbond executives were not available for comment.