An object of one embodiment of the present invention is to provide a semiconductor device with a novel structure in which stored data can be stored even when power is not supplied in a data storing time and there is no limitation on the number of times of writing. The semiconductor device includes a first transistor which includes a first channel formation region using a semiconductor material other than an oxide semiconductor, a second transistor which includes a second channel formation region using an oxide semiconductor material, and a capacitor. One of a second source electrode and a second drain electrode of the second transistor is electrically connected to one electrode of the capacitor.

An object is to provide a deposition method in which a gallium oxide film is formed by a DC sputtering method. Another object is to provide a method for manufacturing a semiconductor device using a gallium oxide film as an insulating layer such as a gate insulating layer of a transistor. An insulating film is formed by a DC sputtering method or a pulsed DC sputtering method, using an oxide target including gallium oxide (also referred to as GaO.sub.X). The oxide target includes GaO.sub.X, and X is less than 1.5, preferably more than or equal to 0.01 and less than or equal to 0.5, further preferably more than or equal to 0.1 and less than or equal to 0.2. The oxide target has conductivity, and sputtering is performed in an oxygen gas atmosphere or a mixed atmosphere of an oxygen gas and a rare gas such as argon.

A memory device with excellent writing performance and excellent storing performance is provided. In the memory device, a first layer overlaps with a second layer. The first layer includes a first transistor including an oxide semiconductor as an active layer. The second layer includes a second transistor and a third transistor each including an oxide semiconductor as an active layer. The off-state current of a transistor formed in the first layer is lower than the off-state current of each of a transistor formed in the second layer. The field-effect mobility of the transistor formed in the second layer is higher than the field-effect mobility of the transistor formed in the first layer.

An object is to provide a semiconductor device with a novel structure. The semiconductor device includes a first wiring; a second wiring; a third wiring; a fourth wiring; a first transistor having a first gate electrode, a first source electrode, and a first drain electrode; and a second transistor having a second gate electrode, a second source electrode, and a second drain electrode. The first transistor is provided in a substrate including a semiconductor material. The second transistor includes an oxide semiconductor layer.

Provided is a semiconductor structure including a substrate, an isolation structure, a fuse and two gate electrodes. The isolation structure is located in the substrate and defines active regions of the substrate. The fuse is disposed on the isolation structure. The gate electrodes are disposed on the active regions and connected to ends of the fuse. In an embodiment, a portion of a bottom surface of the fuse is lower than top surfaces of the active regions of the substrate.

A semiconductor device is described, which includes a first transistor, a second transistor, and a capacitor. The second transistor and the capacitor are provided over the first transistor so as to overlap with a gate of the first transistor. A semiconductor layer of the second transistor and a dielectric layer of the capacitor are directly connected to the gate of the first transistor. The second transistor is a vertical transistor, where its channel direction is perpendicular to an upper surface of a semiconductor layer of the first transistor.

Disclosed is a semiconductor device capable of functioning as a memory device. The memory device comprises a plurality of memory cells, and each of the memory cells contains a first transistor and a second transistor. The first transistor is provided over a substrate containing a semiconductor material and has a channel formation region in the substrate. The second transistor has an oxide semiconductor layer. The gate electrode of the first transistor and one of the source and drain electrodes of the second transistor are electrically connected to each other. The extremely low off current of the second transistor allows the data stored in the memory cell to be retained for a significantly long time even in the absence of supply of electric power.

A transistor which is resistant to a short-channel effect is provided. The transistor includes a first conductor in a ring shape, an oxide semiconductor including a region extending through an inside of a ring of the first conductor, a first insulator between the first conductor and the oxide semiconductor, a second insulator between the first conductor and the first insulator, and a charge trap layer inside the ring of the first conductor. The charge trap layer is inside the second insulator and configured to be in a floating state.

In some examples, an integrated circuit comprises a first plate, a second plate, and a dielectric layer disposed between the first and second plates, the first and second plates and the dielectric layer forming a vertical capacitor, wherein the first and second plates and the dielectric layer of the vertical capacitor are disposed on an isolation region of the integrated circuit.

A non-volatile memory includes cells arranged in rows and columns. Each memory cell includes an access portion and a control portion. The access and control portions share an electrically floating layer of conductive material defining a first capacitive coupling with the access portion and a second capacitive coupling with the control portion. The first capacitive coupling defines a first capacity lower than a second capacity defined by the second capacitive coupling. The control portion is configured so that an electric current extracts charge carriers from the electrically floating layer through Fowler-Nordheim tunneling to store a first logic value in the memory cell. The access portion is configured so that an electric current injects charge carriers in the electrically floating layer by injection of band-to-band tunneling-induced hot electrons to store a second logic value, respectively, in the memory cell.