Synopsys Inc., the biggest supplier of software used to design semiconductors, is under investigation by the U.S. Department of Commerce (DOC) for possibly passing key technology to banned Chinese companies, according to people familiar with the matter. It is said that Investigators are looking into allegations that Synopsys, working with affiliates in China, provided chip designs and software to Huawei Technologies Co.’s HiSilicon unit （华为的海思半导体部门） for manufacture at Semiconductor Manufacturing International Corp.（SMIC，即中芯国际集成电路制造有限公司）Yet the details of the process haven’t been made public. U.S. companies are barred from selling some types of technology to Huawei and SMIC because they’ve been designated as threats to national security by the Commerce Department’s Bureau of Industry and Security. In December Synopsys disclosed it had received a subpoena from BIS relating to “transactions with certain Chinese entities,” without specifying when it received the request or providing further details. At the time, the company said it was in compliance with all regulations and was working to respond to the inquiry.