A semiconductor device excellent in writing operation is provided. In a structure where a data voltage supplied to a source line is supplied to a node of a memory cell via a bit line, a switch is provided between memory cells connected to the bit line. During a period in which the data voltage is supplied to the node of the memory cell, the switch on the bit line, which is provided between the memory cells, is off. With such a structure, parasitic capacitance of the bit line during a period in which the data voltage is supplied to the node of the memory cell can be reduced. As a result, writing of the data voltage into the memory cell can be performed fast.