SWITCH DEVICE AND MEMORY UNIT

A switch device of one embodiment of the present disclosure includes a first electrode, a second electrode disposed to be opposed to the first electrode, and a switch layer provided between the first electrode and the second electrode and including a first element selected from germanium and silicon, a second element selected from arsenic, phosphorus, and antimony, and a third element selected from selenium and tellurium. The switch layer includes at least one first layer and at least one second layer that are stacked. The first layer includes at least one kind of the second element and at least one kind of the third element, includes the third element in a range of 50 atomic % or more and 80 atomic % or less in composition ratio, and is negative in temperature dependence of a threshold voltage. The second layer includes at least one kind of the first element and at least one kind of the third element, includes the first element in a range of 20 atomic % or more and 50 atomic % or less in composition ratio, and is positive in temperature dependence of the threshold voltage.