A semiconductor device with a novel structure is provided, which can hold stored data even when no power is supplied and which has no limitations on the number of writing operations. A semiconductor device is formed using a material which enables off-state current of a transistor to be reduced significantly; e.g., an oxide semiconductor material which is a wide-gap semiconductor. With use of a semiconductor material which enables off-state current of a transistor to be reduced significantly, the semiconductor device can hold data for a long period. In a semiconductor device with a memory cell array, parasitic capacitances generated in the nodes of the first to the m-th memory cells connected in series are substantially equal, whereby the semiconductor device can operate stably.