SEMICONDUCTOR STORAGE DEVICE

To provide a semiconductor storage device that operates at high speed.SOLUTION: A semiconductor storage device includes: first and second electrodes; a selector layer connected between the first and second electrodes and capable of transiting to first and second states having first and second resistance values; and a phase change layer connected between the selector layer and the first electrode and capable of transiting to third and fourth states having third and fourth resistance values. The selector layer transits to the first state at a voltage equal to or greater than a first threshold voltage and to the second state at a voltage lower than a hold voltage that can maintain the first state. The phase change layer is arranged between the first and second electrodes to transit to the third state at a voltage between the first voltage greater than the first threshold voltage and a second voltage greater than the first voltage and to transit to the fourth state at the voltage equal to or greater than the third voltage greater than the second voltage, and not to transit to either state at the voltage greater than the second voltage and lower than the third voltage. In a set operation of transiting the phase change layer from the fourth state to the third state, a set voltage equal to or higher than the first voltage and equal to or lower than the second voltage is supplied between the first and second electrodes.SELECTED DRAWING: Figure 6 【課題】高速に動作する半導体記憶装置を提供する。【解決手段】半導体記憶装置は、第１、第２電極と、第１、第２電極の間に接続され、第１、第２の抵抗値を有する第１、第２の状態に遷移可能なセレクタ層と、セレクタ層及び第１電極の間に接続され、第３、第４の抵抗値を有する第３、第４の状態に遷移可能な相変化層とを備える。セレクタ層は、第１閾値電圧以上で第１の状態に、第１の状態に維持可能なホールド電圧より小さい電圧で第２の状態に遷移する。相変化層は、第１、第２電極の間に、第１閾値電圧より大きい第１電圧から第１電圧より大きい第２電圧の間の電圧で第３の状態に、第２電圧より大きい第３電圧以上で第４の状態に遷移し、第２電圧より大きく第３電圧より小さい電圧ではいずれの状態へも遷移しない。相変化層を第４から第３の状態に遷移させるセット動作では、第１、第２電極の間に、第１電圧以上、第２電圧以下のセット電圧を供給する。【選択図】図６