TECHNICAL FIELD

One embodiment of the present invention relates to a semiconductor device. One embodiment of the present invention relates to, in particular, a semiconductor device capable of imitating human brain's storage of information.

In this specification and the like, a semiconductor device generally refers to devices that can function by utilizing semiconductor characteristics.

BACKGROUND ART

A von Neumann computer, which is used in development of artificial intelligence (AI) has been overwhelming humans in terms of calculation speed.

By contrast, human brains are capable of making a right judgment by comparing fragmentary input information and memory and supplementing the information. Human brains are also capable of solving a problem, which is difficult for a computer, through association with memories from a wide range of fields or by using creativity and foresight.

With improvement in computer performance in recent years, large-scale calculation such as learning and inference with the use of a neural network has become possible. In addition, drastic improvement in computer's recognition accuracy with the use of deep learning in a field of machine learning has been reported (see Patent Document 1, for example). In fields that require creativity and foresight, such as shogi and go, problems that used to be difficult for computers have now become possible to be solved by computers.

REFERENCE

Patent Document

[Patent Document 1] United States Patent Application Publication No. 2016/0110642

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

The capability of conventional artificial intelligence devices falls far short of human brains in terms of power efficiency. In hardware such as CPU and GPU, arithmetic processing is performed while storing data by using memory elements such as SRAM and DRAM, which are made up of Si transistors. The downsizing of memory elements made up of Si transistors resulted in increase of leakage current, and along with increase of the circuit scale for higher computer performance, resulted in further increase in power consumption.

Furthermore, the information storing function of memory elements of conventional artificial intelligence devices is uniform. For example, most of memory elements such as SRAM and DRAM write/read data of 0 or 1. By contrast, human brains have variety of information storage, including information storing methods such as long-term memory and short-term memory, and transfer of information storing locations such as memory at the cerebral neocortex and memory at the hippocampus.

An object of one embodiment of the present invention is to provide a semiconductor device with a novel structure. Another object of one embodiment of the present invention is to provide a semiconductor device that can operate with lower power consumption. Another object of one embodiment of the present invention is to provide a semiconductor device capable of imitating human brain's storage of information.

Note that the description of these objects does not preclude the existence of other objects. In one embodiment of the present invention, there is no need to achieve all the objects. In addition, other objects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.

Means for Solving the Problems

One embodiment of the present invention is a semiconductor device including a control unit, a memory unit, and a sensor unit, in which the memory unit includes a memory circuit and a switching circuit, the memory circuit includes a first transistor and a capacitor, the switching circuit includes a second transistor and a third transistor, the first transistor and the second transistor include a semiconductor layer including a channel formation region with an oxide semiconductor, and the control unit has a function of switching a signal supplied to the first transistor and the second transistor, in accordance with a signal obtained at the sensor unit.

One embodiment of the present invention is a semiconductor device including a control unit, a memory unit, and a sensor unit, in which the memory unit includes a memory circuit and a switching circuit, the memory circuit includes a first transistor and a capacitor, the switching circuit includes a second transistor and a third transistor, the first transistor and the second transistor include a semiconductor layer including a channel formation region with an oxide semiconductor, and a back gate electrode, and the control unit has a function of switching a signal supplied to the back gate electrode, in accordance with a signal obtained at the sensor unit.

One embodiment of the present invention is a semiconductor device including a control unit, a memory unit, and a sensor unit, in which the memory unit includes a memory circuit and a switching circuit, the memory circuit includes a first transistor and a capacitor, one of a source and a drain of the first transistor is electrically connected to one electrode of the capacitor, the switching circuit includes a second transistor and a third transistor, one of a source and a drain of the second transistor is electrically connected to a gate of the third transistor, the first transistor and the second transistor include a semiconductor layer including a channel formation region with an oxide semiconductor, and a back gate electrode, and the control unit has a function of switching a signal supplied to the back gate electrode, in accordance with a signal obtained at the sensor unit.

One embodiment of the present invention is a semiconductor device including a control unit, a memory unit, and a sensor unit, in which the memory unit includes a memory circuit and a switching circuit, the memory circuit includes a first transistor and a capacitor, the switching circuit includes a second transistor and a third transistor, the first transistor and the second transistor include a semiconductor layer including a channel formation region with an oxide semiconductor, and a gate electrode, and the control unit has a function of switching a signal supplied to the gate electrode, in accordance with a signal obtained at the sensor unit.

One embodiment of the present invention is a semiconductor device including a control unit, a memory unit, and a sensor unit, in which the memory unit includes a memory circuit and a switching circuit, the memory circuit includes a first transistor and a capacitor, one of a source and a drain of the first transistor is electrically connected to one electrode of the capacitor, the switching circuit includes a second transistor and a third transistor, one of a source and a drain of the second transistor is electrically connected to a gate of the third transistor, the first transistor and the second transistor include a semiconductor layer including a channel formation region with an oxide semiconductor, and a gate electrode, and the control unit has a function of switching a signal supplied to the gate electrode, in accordance with a signal obtained at the sensor unit.

In one embodiment of the present invention, a semiconductor device in which the memory circuit includes a fourth transistor, and one of the source and the drain of the second transistor is electrically connected to a gate of the fourth transistor is preferable.

Effect of the Invention

According to one embodiment of the present invention, a semiconductor device with a novel structure can be provided. According to one embodiment of the present invention, a semiconductor device that can operate with low power consumption can also be provided. One object of one embodiment of the present invention is to provide a semiconductor device capable of imitating human brain's storage of information.

Note that the description of the effects does not preclude the existence of other effects. In one embodiment of the present invention, there is no need to achieve all the effects. Other effects will be apparent from and can be derived from the descriptions of the specification, the drawings, the claims, and the like.

