The memory chip sector is trading lower, driven by a sharp decline in market-leader Samsung Electronics. Shares of the world's largest memory chip maker fell over 8% after it announced a record shareholder return plan of up to $79 billion. While substantial, the amount fell short of high investor expectations, especially following a more aggressive buyback announcement from competitor SK Hynix. This disappointment with the sector bellwether is weighing on memory chip stocks globally during the pre-market session.