Spurred by a Semiconductor Industry Association petition, U.S. Trade Representative Clayton Yeutter launched an investigation yesterday into possible trade violations by Japan's microchip manufacturers.

The SIA filed a petition on June 14 under Section 301 of the 1974 Trade Act charging that Japanese manufacturers shut American manufacturers out of their market while selling Japanese microchips in this country at low prices designed to shut down American competitors.

"The industry's petition raises serious questions about possible Japanese market barriers in microelectronics that deserve a thorough investigation," said Yeutter, who was sworn in as trade representative last week.

"The petition's portrayal of the semiconductor industry and market structure in the U.S. and Japan skews reality to serve the interests of but one segment of semiconductor manufacturing in the United States," said Akio Morita, chairman of the Sony Corp. and of the Electronic Industries Association of Japan.

He said that the U.S. lack of market share stems from the vertical integration of Japanese companies, which choose to buy semiconductors from their own firms. Low performance of American goods overseas has also been linked to the performance of a strong dollar against a weaker yen.

The trade representative's office has up to a year to investigate the petition and may recommend that the president impose retaliatory restrictions on Japan's exports to the U.S. Yeutter said that the USTR staff will be meeting with Japanese officials "shortly."

"We have been victimized by predatory pricing and we seem to have now gotten the attention of the higher levels of government," said Elliott Sopkin, vice president of communications at Advanced Micro Devices Inc., which he says is the ninth-largest producer of semiconductors in the world.

"If we lose semiconductors the way we lost steel and automobiles, we're going to lose high technology," Sopkin said.

While sales at Advanced Micro Design grew 63 percent last year, Sopkin said that the company's sales are dropping because of both the soft market and intense Japanese competition with AMD's product line. Sales for the quarter ended Sept. 31 were $257 million, but Sopkin indicated that sales for the last quarter ended June 31, which have not been officially reported, will only be about $160 million.

According to In-Stat, a Scottsdale, Ariz., market research company, Japan holds 15 percent of the $11.6 billion American market in semiconductors and Europeans have about eight percent. U.S. manufacturers command the rest. The SIA claims that U.S. firms have only held about 10 percent of what In-Stat calls an $8 billion market in Japan, but Japanese companies and officials contend that the United States actually holds a little over 19 percent of the Japanese market.

Some of the most intense competition has come in the field of memory products. According to SIA and Dataquest, a market research firm based in San Jose, Calif., prices for a 256K programmable microchip have plummeted from $158 per chip to a few dollars each in some cases. In-Stat reports that a lower-capacity memory chip, a 64K DRAM, can be bought in bulk for as little as 40 cents a chip.