The U.S. International Trade Commission (ITC) has voted to investigate complaints by two U.S. companies that 18 other companies are violating their patent for semiconductor chips containing tungsten metal.

LSI of Milpitas, California, and its subsidiary Agere Systems have asked the ITC to bar imports of semiconductors containing tungsten by companies including National Semiconductor, based in Santa Clara, California, Integrated Device Technology of San Jose and Elpida Memory, based in Japan.

LSI and Agere Systems also want the ITC to issue "cease and desist orders prohibiting the importation, sale, offer for sale, advertising, or the soliciting of the sale of semiconductor devices encompassed by the claims," the companies said in their complaint, filed on April 18.

LSI and Agere Systems say they have a July 1993 patent for using tungsten, along with a glue layer, to manufacture several types of electronic devices, including semiconductors. The companies have brought several lawsuits in an effort to enforce their patent, and they are facing a recent lawsuit asking that the patent be invalidated.

The ITC's decision to pursue an investigation is a first step in determining whether patent infringement has occurred. The case will be referred to an ITC administrative law judge, who will hold an evidentiary hearing. The judge will make an initial determination about whether there has been a violation of the so-called section 337 trade laws, and the judge's decision is subject to review by the ITC.

Representatives of National Semiconductor and Integrated Device Technology weren't immediately available for comment.