Signal processing circuit and method for driving the same
View Patent ↗It is an object to provide a memory device for which a complex manufacturing process is not necessary and whose power consumption can be suppressed and a signal processing circuit including the memory device. In a memory element including a phase-inversion element by which the phase of an input signal is inverted and the signal is output such as an inverter or a clocked inverter, a capacitor which holds data and a switching element which controls storing and releasing of electric charge in the capacitor are provided. For the switching element, a transistor including an oxide semiconductor in a channel formation region is used. The memory element is applied to a memory device such as a register or a cache memory included in a signal processing circuit.
1. A signal processing circuit comprising:
an arithmetic circuit; and
a memory device configured to store data from the arithmetic circuit,
wherein the memory device comprises a plurality of memory elements,
wherein each of the plurality of memory elements comprises:
a pair of logic elements configured to hold the data by connection of an output terminal of one of the pair of logic elements to an input terminal of the other of the pair of logic elements and an output terminal of the other of the pair of logic elements to an input terminal of the one of the pair of logic elements,
a capacitor,
a first transistor,
a second transistor, and
a third transistor which includes a oxide semiconductor in a channel formation region and is configured to control writing of the data to the capacitor,
wherein one of a source and a drain of the first transistor is electrically connected to the input terminal of the one of the pair of logic elements, one of a source and a drain of the second transistor, and one of a source and a drain of the third transistor,
wherein the other of the source and the drain of the second transistor is electrically connected to the output terminal of the other of the pair of logic elements,
wherein the other of the source and the drain of the third transistor is electrically connected to one electrode of the capacitor, and
wherein the pair of logic elements comprise at least one of an inverter and a clocked inverter.
2. The signal processing circuit according to claim 1 , wherein off-state current density of the third transistor is less than or equal to 100 zA/mm.
3. The signal processing circuit according to claim 1 , wherein the oxide semiconductor is an In-Ga-Zn-O-based oxide semiconductor.
4. The signal processing circuit according to claim 1 , wherein a hydrogen concentration of the third channel formation region is less than or equal to 5×10 19 /cm 3 .
5. The signal processing circuit according to claim 1 , wherein the signal processing circuit is selected from the group consisting of an LSI comprising a CPU, a DSP and a microcontroller.
6. A method for driving a signal processing circuit comprising:
an arithmetic circuit; and
a memory device configured to store data from the arithmetic circuit,
wherein the memory device comprises a memory element,
wherein the memory element comprises:
a pair of logic elements configured to hold the data by connection of an output terminal of one logic element to an input terminal of the other logic element and an output terminal of the other logic element to an input terminal of the one logic element,
a capacitor,
a first transistor,
a second transistor, and
a third transistor which includes a oxide semiconductor in a channel formation region and is configured to control writing of the data to the capacitor,
wherein one of a source and a drain of the first transistor is electrically connected to the input terminal of the one logic element, one of a source and a drain of the second transistor, and one of a source and a drain of the third transistor,
wherein the other of the source and the drain of the second transistor is electrically connected to the output terminal of the other logic element,
wherein the other of the source and the drain of the third transistor is electrically connected to one electrode of the capacitor, and
wherein the pair of logic elements comprise at least one of an inverter and a clocked inverter,
the method comprising the steps of:
writing data from the arithmetic circuit into the memory element;
writing data into the capacitor by turning on the third transistor;
turning off the third transistor after the writing data into the capacitor; and
stopping supply of power supply voltage to the arithmetic circuit and the memory device.
7. A method for driving a signal processing circuit comprising:
a plurality of arithmetic circuits; and
a memory device configured to store data from the plurality of arithmetic circuits,
wherein the memory device comprises a memory element,
wherein the memory element comprises:
a pair of logic elements configured to hold the data by connection of an output terminal of one logic element to an input terminal of the other logic element and an output terminal of the other logic element to an input terminal of the one logic element,
a capacitor,
a first transistor,
a second transistor, and
a third transistor which includes a oxide semiconductor in a channel formation region and is configured to control writing of the data to the capacitor,
wherein one of a source and a drain of the first transistor is electrically connected to the input terminal of the one logic element, one of a source and a drain of the second transistor, and one of a source and a drain of the third transistor,
wherein the other of the source and the drain of the second transistor is electrically connected to the output terminal of the other logic element,
wherein the other of the source and the drain of the third transistor is electrically connected to one electrode of the capacitor, and
wherein the pair of logic elements comprise at least one of an inverter and a clocked inverter,
the method comprising the steps of:
writing data from one arithmetic circuit of the plurality of arithmetic circuits into the memory element;
writing data into the capacitor by turning on the third transistor;
turning off the third transistor after the writing data into the capacitor; and
stopping supply of power supply voltage to the one arithmetic circuit and the memory device.
8. A semiconductor device comprising:
a memory element comprising a first transistor, a second transistor, a third transistor, a capacitor, a first logic element comprising at least one of an inverter and a clocked inverter, and a second logic element comprising at least one of an inverter and a clocked inverter,
wherein one of a source and a drain of the first transistor is electrically connected to an input terminal of the first logic element, one of a source and a drain of the second transistor, and one of a source and a drain of the third transistor,
wherein the other of the source and the drain of the second transistor is electrically connected to an output terminal of the second logic element,
wherein the other of the source and the drain of the third transistor is electrically connected to one electrode of the capacitor,
wherein the input terminal of the first logic element is electrically connected to the output terminal of the second logic element through the second transistor,
wherein an input terminal of the second logic element is electrically connected to an output terminal of the first logic element,
wherein the third transistor comprises an oxide semiconductor in a channel formation region.
9. The semiconductor device according to claim 8 , further comprising an arithmetic circuit,
wherein the memory element is configured to store data from the arithmetic circuit.
10. The semiconductor device according to claim 8 , wherein off-state current density of the third transistor is less than or equal to 100 zA/mm.
11. The semiconductor device according to claim 8 , wherein the oxide semiconductor is an In-Ga-Zn-O-based oxide semiconductor.
12. The semiconductor device according to claim 8 , wherein the semiconductor device is selected from the group consisting of an LSI comprising a CPU, a DSP and a microcontroller.