An object is to reduce leakage current and parasitic capacitance of a transistor used for an LSI, a CPU, or a memory. A semiconductor integrated circuit included in an LSI, a CPU, or a memory is manufactured using the transistor which is formed using an oxide semiconductor which is an intrinsic or substantially intrinsic semiconductor obtained by removal of impurities which serve as electron donors (donors) from the oxide semiconductor and has larger energy gap than a silicon semiconductor, and is formed over a semiconductor substrate. With the transistor which is formed over the semiconductor substrate and includes the highly purified oxide semiconductor layer with sufficiently reduced hydrogen concentration, a semiconductor device whose power consumption due to leakage current is low can be realized.

A method for forming a semiconductor device includes forming a fin device structure in a buffer layer on a substrate. The fin device structure includes a lower portion extending over the silicon substrate and a fin structure protruding above the lower portion. The method also includes forming a sacrificial layer disposed over the fin device structure and forming a device semiconductor layer disposed over a surface of the sacrificial layer. A gate dielectric layer is then formed and is disposed over a surface of the device semiconductor layer. A gate electrode layer is formed and disposed over a surface of the gate dielectric layer. The method includes removing a portion of the sacrificial layer to form a cavity surrounding the fin structure and performing an oxidation process to form a thermal oxide layer in the cavity surrounding the side surface of the fin structure.

According to one example embodiment, a structure includes at least one SOI (semiconductor-on-insulator) transistor situated over a buried oxide layer, where the buried oxide layer overlies a bulk substrate. The structure further includes an electrically charged field control ring situated over the buried oxide layer and surrounding the at least one SOI transistor. A width of the electrically charged field control ring is greater than a thickness of the buried oxide layer. The electrically charged field control ring reduces a conductivity of a surface portion of the bulk substrate underlying the field control ring, thereby reducing RF coupling of the at least one SOI transistor through the bulk substrate. The structure further includes an isolation region situated between the electrically charged field control ring and the at least one SOI transistor. A method to achieve and implement the disclosed structure is also provided.

To provide a transistor in which a channel is formed in an oxide semiconductor and which has stable electrical characteristics. To suppress shift in threshold voltage of a transistor in which a channel is formed in an oxide semiconductor. To provide a normally-off switching element having a positive threshold voltage as an n-channel transistor in which a channel is formed in an oxide semiconductor. A base insulating layer is formed over a substrate, an oxide semiconductor layer is formed over the base insulating layer, a first gate insulating layer is formed over the oxide semiconductor layer, a second gate insulating layer is formed over the first gate insulating layer by a sputtering method or an atomic layer deposition method at a substrate temperature of higher than or equal to 100 C., and a gate electrode layer is formed over the second gate insulating layer.

An object is to reduce leakage current and parasitic capacitance of a transistor used for an LSI, a CPU, or a memory. A semiconductor integrated circuit such as an LSI, a CPU, or a memory is manufactured using a thin film transistor in which a channel formation region is formed using an oxide semiconductor which becomes an intrinsic or substantially intrinsic semiconductor by removing impurities which serve as electron donors (donors) from the oxide semiconductor and has larger energy gap than that of a silicon semiconductor. With use of a thin film transistor using a highly purified oxide semiconductor layer with sufficiently reduced hydrogen concentration, a semiconductor device with low power consumption due to leakage current can be realized.

A thin film transistor array substrate includes a glass substrate and a plurality of TFTs thereon. Each TFT includes a gate formed on the glass substrate, a gate insulating layer covering the gate, an active layer formed on the gate insulating layer, a source on the active layer, and a drain on the active layer. A gap is between the source and the drain in a first direction. An area of the active layer that matches the gap is a channel. A plurality of protrusions and recesses on a coarse surface of the gate insulating layer face the active layer, at least within the area corresponding to the channel. The active layer fits with the gate insulting layer. The present invention also proposes a method for manufacturing the thin film transistor array substrate and a liquid crystal display panel having the thin film transistor array substrate.

A liquid crystal display device is provided in which the aperture ratio can be increased in a pixel including a thin film transistor in which an oxide semiconductor is used. In the liquid crystal display device, the thin film transistor including a gate electrode, a gate insulating layer and an oxide semiconductor layer which are provided so as to overlap with the gate electrode, and a source electrode and a drain electrode which overlap part of the oxide semiconductor layer is provided between a signal line and a pixel electrode which are provided in a pixel portion. The off-current of the thin film transistor is 110.sup.13 A or less. A potential can be held only by a liquid crystal capacitor, without a capacitor which is parallel to a liquid crystal element, and a capacitor connected to the pixel electrode is not formed in the pixel portion.

A display device includes a first electrode, a first insulating layer having a first top surface and a first side wall, the first side wall having a closed shape and being exposed to a first opening reaching the first electrode, an oxide semiconductor layer on the first side wall, the oxide semiconductor layer including a first portion and a second portion, the first portion being connected with the first electrode, a gate electrode facing the oxide semiconductor layer, a gate insulating layer between the oxide semiconductor layer and the gate electrode, a first transparent conductive layer above the first top surface, the first transparent conductive layer being connected with the second portion, and a second transparent conductive layer connected with the first transparent conductive layer, the second transparent conductive layer forming the same layer with the first transparent conductive layer.

A change in electrical characteristics can be inhibited and reliability can be improved in a semiconductor device including an oxide semiconductor. The semiconductor device including an oxide semiconductor film includes a first insulating film, the oxide semiconductor film over the first insulating film, a second insulating film over the oxide semiconductor film, and a third insulating film over the second insulating film. The second insulating film includes oxygen and silicon, the third insulating film includes nitrogen and silicon, and indium is included in a vicinity of an interface between the second insulating film and the third insulating film.

A semiconductor device including a transistor in which an oxide semiconductor is used for a channel formation region and which has a positive threshold voltage to serve as a normally-off switching element, and the like are provided. Stable electrical characteristics are given to the semiconductor device including the transistor in which an oxide semiconductor film is used for the channel formation region, and thus the semiconductor device has high reliability. In a semiconductor device including a transistor in which an oxide semiconductor film including a channel formation region, source and drain electrode layers, a gate insulating film, and a gate electrode layer are stacked in this order over an oxide insulating film, a conductive layer overlapping with the gate electrode layer with the channel formation region provided therebetween and controlling the electrical characteristics of the transistor is provided in the oxide insulating film including an oxygen excess region.