Disclosed is a preparation method for a semiconductor structure. The semiconductor structure includes: a substrate; an epitaxial layer and an epitaxial structure that are stacked on the substrate in sequence. The epitaxial layer is doped with a doping element. In the forming process, a sacrificial layer is formed on the epitaxial layer, and the sacrificial layer is repeatedly etched, such that a concentration of the doping element in the epitaxial layer is lower than a preset value. In this application, the sacrificial layer is formed on the epitaxial layer, and the sacrificial layer is repeatedly etched, such that the concentration of the doping element in the epitaxial layer is lower than the preset value, so as to prevent the doping element in the epitaxial layer from being precipitated upward into an upper-layer structure, ensure the mobility of electrons in a channel layer, and improve the performance of a device.

A semiconductor device with a small variation in characteristics is provided. The semiconductor device includes a first insulator; a second insulator having an opening over the first insulator; a third insulator that has a first depressed portion and is provided inside the opening; a first oxide that has a second depressed portion and is provided inside the first depressed portion; a second oxide provided inside the second depressed portion; a first conductor and a second conductor that are electrically connected to the second oxide and are apart from each other; a fourth insulator over the second oxide; and a third conductor including a region overlapping with the second oxide with the fourth insulator therebetween. The second oxide includes a first region, a second region, and a third region sandwiched between the first region and the second region in a top view. The first conductor includes a region overlapping with the first region and the second insulator. The second conductor includes a region overlapping with the second region and the second insulator. The third conductor includes a region overlapping with the third region.

A semiconductor device and a method of forming the same are provided. The semiconductor device includes a gate stack over an active region and a source/drain region in the active region adjacent the gate stack. The source/drain region includes a first semiconductor layer having a first germanium concentration and a second semiconductor layer over the first semiconductor layer. The second semiconductor layer has a second germanium concentration greater than the first germanium concentration. The source/drain region further includes a third semiconductor layer over the second semiconductor layer and a fourth semiconductor layer over the third semiconductor layer. The third semiconductor layer has a third germanium concentration greater than the second germanium concentration. The fourth semiconductor layer has a fourth germanium concentration less than the third germanium concentration.

A photonic structure can include in one aspect one or more waveguides formed by patterning of waveguiding material adapted to propagate light energy. Such waveguiding material may include one or more of silicon (single-, poly-, or non-crystalline) and silicon nitride.

A two-dimensional semiconductor transistor includes a gate electrode, a gate insulating layer disposed on the gate electrode, an organic dopant layer disposed on the gate insulating layer and comprising an organic material including electrons, a two-dimensional semiconductor layer disposed on the organic dopant layer, a source electrode disposed on the two-dimensional semiconductor layer, and a drain electrode disposed on the two-dimensional semiconductor layer and spaced apart from the source electrode. A hysteresis of the two-dimensional semiconductor transistor is reduced due to the two-dimensional semiconductor transistor including the organic dopant layer.

A thin-film storage transistor includes (a) first and second semiconductor regions comprising polysilicon of a first conductivity; and (b) a channel region between the first and second semiconductor regions, the channel region comprising single-crystal epitaxial grown silicon, and wherein the thin-film storage transistor is formed above a monocrystalline semiconductor substrate.

A high-quality crystalline film having less impurity of Si and the like and useful in semiconductor devices is provided. A crystalline film containing a crystalline metallic oxide including gallium as a main component, wherein the crystalline film includes a Si in a content of 2×10.sup.15 cm.sup.−3 or less.

A III-nitride-based semiconductor device is provided. The III-nitride semiconductor device includes a silicon substrate having a surface with a periodic array of recesses formed therein. A discontinuous insulating layer is formed within each recess of the periodic array of recesses such that a portion of the silicon substrate surface between adjacent recesses is free from coverage of the discontinuous insulating layer. A first epitaxial III-nitride semiconductor layer is formed over the silicon substrate with the periodic array of recesses and discontinuous insulating layer formed thereon. A second III-nitride semiconductor layer is disposed over the first III-nitride semiconductor layer and has a bandgap greater than a bandgap of the first III-nitride semiconductor layer. At least one source and at least one drain are disposed over the second III-nitride semiconductor layer. A gate is also disposed over the second III-nitride semiconductor layer between the source and the drain.

A semiconductor device and a method of forming the same are provided. The semiconductor device includes a gate stack over an active region and a source/drain region in the active region adjacent the gate stack. The source/drain region includes a first semiconductor layer having a first germanium concentration and a second semiconductor layer over the first semiconductor layer. The second semiconductor layer has a second germanium concentration greater than the first germanium concentration. The source/drain region further includes a third semiconductor layer over the second semiconductor layer and a fourth semiconductor layer over the third semiconductor layer. The third semiconductor layer has a third germanium concentration greater than the second germanium concentration. The fourth semiconductor layer has a fourth germanium concentration less than the third germanium concentration.

In a silicon carbide substrate including: a SiC substrate; and a first semiconductor layer, a second semiconductor layer and a drift layer that are epitaxial layers sequentially formed on the SiC substrate, an impurity concentration of the first semiconductor layer is lower than impurity concentrations of the SiC substrate and the second semiconductor layer, and the second semiconductor layer is formed to have a high impurity concentration or a large thickness.