US Patent 9514792 Semiconductor device having stacked layers

A semiconductor device is disclosed in which there are provided a first substrate including memory cells and at least one bit line electrically coupled to the memory cells, and a second substrate including a sense amplifier. Each of the memory cells includes a first transistor, and the sense amplifier includes a second transistor. The second substrate is stacked with the first substrate such that the sense amplifier amplifies data transferred through the bit line from a selected one of the memory cells. The first transistor is lower in carrier mobility than the second transistor.