Semiconductor device and driving method thereof

A semiconductor device comprising:

• a memory cell array including memory cells arranged in matrix;
• and
• a refresh timing detection circuit operationally connected to the memory cell array, the refresh timing detection circuit including a reference cell and a comparator,
• wherein each of the memory cells includes a first transistor including a first oxide semiconductor and a first capacitor electrically connected to the first transistor,
• wherein the reference cell includes a second transistor including a second oxide semiconductor, a second capacitor electrically connected to the second transistor, and a third transistor including a p-type channel electrically connected to the second capacitor, and
• wherein the reference cell is electrically connected to the comparator.

A semiconductor device comprising:

• a memory cell array including memory cells arranged in matrix;
• and
• a refresh timing detection circuit operationally connected to the memory cell array, the refresh timing detection circuit including reference cells and a comparator,
• wherein each of the memory cells includes a first transistor including a first oxide semiconductor and a first capacitor electrically connected to the first transistor,
• wherein each of the reference cells includes a second transistor including a second oxide semiconductor, a second capacitor electrically connected to the second transistor, and a third transistor electrically connected to the second capacitor, and
• wherein the comparator is electrically connected to at least one of the reference cells.