Abstract: Provided is a field-effect transistor (FET) having small off-state current, which is used in a miniaturized semiconductor integrated circuit. The field-effect transistor includes a thin oxide semiconductor which is formed substantially perpendicular to an insulating surface and has a thickness of greater than or equal to 1 nm and less than or equal to 30 nm, a gate insulating film formed to cover the oxide semiconductor, and a strip-like gate which is formed to cover the gate insulating film and has a width of greater than or equal to 10 nm and less than or equal to 100 nm. In this structure, three surfaces of the thin oxide semiconductor are covered with the gate, so that electrons injected from a source or a drain can be effectively removed, and most of the space between the source and the drain can be a depletion region; thus, off-state current can be reduced.

Abstract: An intrinsic or substantially intrinsic semiconductor, which has been subjected to a step of dehydration or dehydrogenation and a step of adding oxygen so that the carrier concentration is less than 1×1012/cm3 is used for an oxide semiconductor layer of an insulated gate transistor, in which a channel region is formed. The length of the channel formed in the oxide semiconductor layer is set to 0.2 ?m to 3.0 ?m inclusive and the thicknesses of the oxide semiconductor layer and the gate insulating layer are set to 15 nm to 30 nm inclusive and 20 nm to 50 nm inclusive, respectively, or 15 nm to 100 nm inclusive and 10 nm to 20 nm inclusive, respectively. Consequently, a short-channel effect can be suppressed, and the amount of change in threshold voltage can be less than 0.5 V in the range of the above channel lengths.

Abstract: A conventional DRAM needs to be refreshed at an interval of several tens of milliseconds to hold data, which results in large power consumption. In addition, a transistor therein is frequently turned on and off; thus, deterioration of the transistor is also a problem. These problems become significant as the memory capacity increases and transistor miniaturization advances. A transistor is provided which includes a wide-gap semiconductor and has a trench structure including a trench for a gate electrode and a trench for element isolation. Even when the distance between a source electrode and a drain electrode is decreased, the occurrence of a short-channel effect can be suppressed by setting the depth of the trench for the gate electrode as appropriate.

Abstract: A semiconductor device in which a circuit and a power storage element are efficiently placed is provided. The semiconductor device includes a first transistor, a second transistor, and an electric double-layer capacitor. The first transistor, the second transistor, and the electric double-layer capacitor are provided over one substrate. A band gap of a semiconductor constituting a channel region of the second transistor is wider than a band gap of a semiconductor constituting a channel region of the first transistor. The electric double-layer capacitor includes a solid electrolyte.

Abstract: A novel display device with higher reliability having a structure of blocking moisture and oxygen, which deteriorate the characteristics of the display device, from penetrating through a sealing region and a method of manufacturing thereof is provided.

Abstract: A structure including an oxide semiconductor layer which is provided over an insulating surface and includes a channel formation region and a pair of low-resistance regions between which the channel formation region is positioned, a gate insulating film covering a top surface and a side surface of the oxide semiconductor layer, a gate electrode covering a top surface and a side surface of the channel formation region with the gate insulating film positioned therebetween, and electrodes electrically connected to the low-resistance regions is employed. The electrodes are electrically connected to at least side surfaces of the low-resistance regions, so that contact resistance with the source electrode and the drain electrode is reduced.

Abstract: Provided is a field-effect transistor (FET) having small off-state current, which is used in a miniaturized semiconductor integrated circuit. The field-effect transistor includes a thin oxide semiconductor which is formed substantially perpendicular to an insulating surface and has a thickness of greater than or equal to 1 nm and less than or equal to 30 nm, a gate insulating film formed to cover the oxide semiconductor, and a strip-like gate which is formed to cover the gate insulating film and has a width of greater than or equal to 10 nm and less than or equal to 100 nm. In this structure, three surfaces of the thin oxide semiconductor are covered with the gate, so that electrons injected from a source or a drain can be effectively removed, and most of the space between the source and the drain can be a depletion region; thus, off-state current can be reduced.

Abstract: A conventional DRAM needs to be refreshed at an interval of several tens of milliseconds to hold data, which results in large power consumption. In addition, a transistor therein is frequently turned on and off; thus, deterioration of the transistor is also a problem. These problems become significant as the memory capacity increases and transistor miniaturization advances. A transistor is provided which includes a wide-gap semiconductor and has a trench structure including a trench for a gate electrode and a trench for element isolation. Even when the distance between a source electrode and a drain electrode is decreased, the occurrence of a short-channel effect can be suppressed by setting the depth of the trench for the gate electrode as appropriate.

Abstract: An object is to increase the on-state current of a thin film transistor. A solution is to provide a projection in a back-channel portion of the thin film transistor. The projection is provided so as to be off a tangent in the back-channel portion between a source or a drain and a channel formation region. With the projection, a portion where electric charge is trapped and a path of the on-state current can be apart from each other, so that the on-state current can be increased. The shape of a side surface of the back-channel portion may be curved, or may be represented as straight lines in a cross section. Further, a method for forming such a shape by performing one etching step is provided.

Abstract: An object is to provide a transistor including an oxide layer which includes Zn and does not include a rare metal such as In or Ga. Another object is to reduce an off current and stabilize electric characteristics in the transistor including an oxide layer which includes Zn. A transistor including an oxide layer including Zn is formed by stacking an oxide semiconductor layer including insulating oxide over an oxide layer so that the oxide layer is in contact with a source electrode layer or a drain electrode layer with the oxide semiconductor layer including insulating oxide interposed therebetween, whereby variation in the threshold voltage of the transistor can be reduced and electric characteristics can be stabilized.

Abstract: An intrinsic or substantially intrinsic semiconductor, which has been subjected to a step of dehydration or dehydrogenation and a step of adding oxygen so that the carrier concentration is less than 1×1012/cm3 is used for an oxide semiconductor layer of an insulated gate transistor, in which a channel region is formed. The length of the channel formed in the oxide semiconductor layer is set to 0.2 ?m to 3.0 ?m inclusive and the thicknesses of the oxide semiconductor layer and the gate insulating layer are set to 15 nm to 30 nm inclusive and 20 nm to 50 nm inclusive, respectively, or 15 nm to 100 nm inclusive and 10 nm to 20 nm inclusive, respectively. Consequently, a short-channel effect can be suppressed, and the amount of change in threshold voltage can be less than 0.5 V in the range of the above channel lengths.

Abstract: Provided is a test method by which a transistor whose reliability is low can be detected with low stress and high accuracy in a shorter period of time than a BT test. Provided is to detect a transistor whose reliability is high in a shorter period of time than a BT test and manufacture an electronic device with high reliability efficiently. Hysteresis characteristics revealed in the result of the Vg-Id measurement with light irradiation to the transistor correlate with the result of a BT test; whether the reliability of the transistor is Good or Not-Good can be judged. Accordingly, the test method by which a transistor whose reliability is low can be detected with low stress and high accuracy in a shorter period of time than a BT test can be provided.

Abstract: A semiconductor device having a highly responsive thin film transistor (TFT) with low subthreshold swing and suppressed decrease in the on-state current and a manufacturing method thereof are demonstrated. The TFT of the present invention is characterized by its semiconductor layer where the thickness of the source region or the drain region is larger than that of the channel formation region. Manufacture of the TFT is readily achieved by the formation of an amorphous semiconductor layer on a projection portion and a depression portion, which is followed by subjecting the melting process of the semiconductor layer, resulting in the formation of a crystalline semiconductor layer having different thicknesses. Selective addition of impurity to the thick portion of the semiconductor layer provides a semiconductor layer in which the channel formation region is thinner than the source or drain region.

Abstract: An object is to reduce to reduce variation in threshold voltage to stabilize electric characteristics of thin film transistors each using an oxide semiconductor layer. An object is to reduce an off current. The thin film transistor using an oxide semiconductor layer is formed by stacking an oxide semiconductor layer containing insulating oxide over the oxide semiconductor layer so that the oxide semiconductor layer and source and drain electrode layers are in contact with each other with the oxide semiconductor layer containing insulating oxide interposed therebetween; whereby, variation in threshold voltage of the thin film transistors can be reduced and thus the electric characteristics can be stabilized. Further, an off current can be reduced.

Abstract: A semiconductor device which includes an oxide semiconductor layer, a source electrode and a drain electrode electrically connected to the oxide semiconductor layer, a gate insulating layer covering the oxide semiconductor layer, the source electrode, and the drain electrode, and a gate electrode over the gate insulating layer is provided. The thickness of the oxide semiconductor layer is greater than or equal to 1 nm and less than or equal to 10 nm. The gate insulating layer satisfies a relation where ?r/d is greater than or equal to 0.08 (nm?1) and less than or equal to 7.9 (nm?1) when the relative permittivity of a material used for the gate insulating layer is ?r and the thickness of the gate insulating layer is d. The distance between the source electrode and the drain electrode is greater than or equal to 10 nm and less than or equal to 1 ?m.

Abstract: An object is to reduce to reduce variation in threshold voltage to stabilize electric characteristics of thin film transistors each using an oxide semiconductor layer. An object is to reduce an off current. The thin film transistor using an oxide semiconductor layer is formed by stacking an oxide semiconductor layer containing insulating oxide over the oxide semiconductor layer so that the oxide semiconductor layer and source and drain electrode layers are in contact with each other with the oxide semiconductor layer containing insulating oxide interposed therebetween; whereby, variation in threshold voltage of the thin film transistors can be reduced and thus the electric characteristics can be stabilized. Further, an off current can be reduced.

Abstract: To reduce oxygen vacancies in an oxide semiconductor film and the vicinity of the oxide semiconductor film and to improve electric characteristics of a transistor including the oxide semiconductor film. A semiconductor device includes a gate electrode whose Gibbs free energy for oxidation is higher than that of a gate insulating film. In a region where the gate electrode is in contact with the gate insulating film, oxygen moves from the gate electrode to the gate insulating film, which is caused because the gate electrode has higher Gibbs free energy for oxidation than the gate insulating film. The oxygen passes through the gate insulating film and is supplied to the oxide semiconductor film in contact with the gate insulating film, whereby oxygen vacancies in the oxide semiconductor film and the vicinity of the oxide semiconductor film can be reduced.

Abstract: A conventional DRAM needs to be refreshed at an interval of several tens of milliseconds to hold data, which results in large power consumption. In addition, a transistor therein is frequently turned on and off; thus, deterioration of the transistor is also a problem. These problems become significant as the memory capacity increases and transistor miniaturization advances. A transistor is provided which includes an oxide semiconductor and has a trench structure including a trench for a gate electrode and a trench for element isolation. Even when the distance between a source electrode and a drain electrode is decreased, the occurrence of a short-channel effect can be suppressed by setting the depth of the trench for the gate electrode as appropriate.

Abstract: A novel display device with higher reliability having a structure of blocking moisture and oxygen, which deteriorate the characteristics of the display device, from penetrating through a sealing region and a method of manufacturing thereof is provided.

Abstract: A transistor includes an island-like semiconductor film over a substrate, and a conductive film forming a gate electrode over the island-like semiconductor film with a gate insulating film interposed therebetween. The semiconductor film includes a channel forming region, a first impurity region forming a source or drain region, and a second impurity region. The channel forming region is overlapped with the gate electrode crossing the island-like semiconductor film. The first impurity region is adjacent to the channel forming region. The second impurity region is adjacent to the channel forming region and the first impurity region. The first impurity region and the second impurity region have different conductivity. The second impurity region and the channel forming region have different conductivity or have different concentration of an impurity element contained in the second impurity region and the channel forming region in a case of having the same conductivity.