Silicon Valley refers to the southern part of Massachusetts.
The eastern region of the San Francisco Bay Area , commonly referred to as the East Bay , includes cities along the eastern shores of the San Francisco Bay and San Pablo Bay . The Santa Clara Valley runs south-southeast from the southern end of San Francisco Bay in Northern California in the United States . Silicon Valley . The region has expanded to include the southern half of the San Francisco Peninsula in San Mateo County , and southern portions of the East Bay in Alameda County .