The invention discloses a semiconductor device and a semiconductor memory device. The semiconductor device can be used as a memory cell and comprises a first p-type semiconductor layer, a first n-type semiconductor layer, a second p-type semiconductor layer and a second n-type semiconductor layer, which are arranged in order. A first data state can be stored in the semiconductor device through applying a forward bias greater than a punch through voltage VBO between the first p-type semiconductor layer and the second n-type semiconductor layer. A second data state can be stored in the semiconductor device through applying a reverse bias in the reverse breakdown zone of the semiconductor device between the first p-type semiconductor layer and the second n-type semiconductor layer. Therefore, the semiconductor device can be effectively used for storing data. The semiconductor memory device includes a memory cell array composed of the semiconductor devices.