Western Digital Corp, a hard-disk drive maker, is acquiring SanDisk Corp for $19 billion that will increase its ability to manufacture flash memory storage chips used in smartphones and tablets. SanDisk shares reached $78.50 on Wednesday, below Western Digital’s offer price of $86.50 in cash and stock. In September, Unisplendour announced it would acquire 15% of Western Digital for $3.78 billion, a transaction that will face regulatory scrutiny over national security concerns. Western Digital’s decision to purchase SanDisk is the latest in a series of deals in the U.S. semiconductor sector, which has endured a recent supply shortage and cheaper products from China that have driven down memory chip prices.