A semiconductor device includes a memory array having a plurality of complementary cells, each including a first memory element and a second memory element, for holding binary data depending on a difference of threshold voltage therebetween, and a control circuit for initializing the complementary cells. The control circuit performs a first initialization control of reducing the threshold voltage of both the first memory element and the second memory element of the complementary cell and changing the threshold voltage of at least one of the first memory element and the second memory element at an intermediate level lower than a first writing level and higher than an initialization level, a first writing control of changing the threshold voltage of one of the first memory element and the second memory element of the complementary cell at the first writing level, and a second initialization control of changing the threshold voltage of both the first memory element and the second memory element of the complementary cell at the initialization level.