An electrical circuit comprising at least two negative capacitance insulators connected in series, one of the two negative capacitance insulators is biased to generate a negative capacitance. One of the negative capacitance insulators may include an air-gap which is part of a nanoelectromechnical system (NEMS) device and the second negative capacitance insulator includes a ferroelectric material. Both of the negative capacitance insulators may be located between the channel and gate of a field effect transistor. The NEMS device may include a movable electrode, a dielectric and a fixed electrode and arranged so that the movable electrode is attached to at least two points and spaced apart from the dielectric and fixed electrode, and the ferroelectric capacitor is electrically connected to either of the electrodes.

A semiconductor device and a method of forming the same are provided. The method includes forming a sacrificial gate structure over an active region. A first spacer layer is formed along sidewalls and a top surface of the sacrificial gate structure. A first protection layer is formed over the first spacer layer. A second spacer layer is formed over the first protection layer. A third spacer layer is formed over the second spacer layer. The sacrificial gate structure is replaced with a replacement gate structure. The second spacer layer is removed to form an air gap between the first protection layer and the third spacer layer.

A method of forming a semiconductor structure includes following steps. A first isolation is formed between a pair of active regions. A gate structure is formed on the first isolation structure. The active regions are etched to form recesses with curved top surfaces. The active regions are etched again to change each of the curved top surfaces to be a top surface and a sidewall substantially perpendicular to the top surface. A pair of contacts is formed respectively on the active regions, such that each of the contacts has a bottom surface and a sidewall substantially perpendicular to the bottom surface.

A semiconductor device includes a semiconductor substrate, multiple trench gate structures and an emitter region. The semiconductor substrate includes: a drift layer of a first conductivity type; a base layer of a second conductivity type disposed on the drift layer; and a collector layer of the second conductivity type, the collector layer disposed at a position opposite to the base layer with the drift layer sandwiched between the base layer and the collector layer. Each of the trench gate structures includes: a trench penetrating the base layer and reaching the drift layer; a gate insulation film is disposed at a wall surface of the trench; and a gate electrode disposed on the gate insulation film. The emitter region is disposed on a surface layer portion of the base layer and is in contact with the trench.

A semiconductor structure includes a first device and a second device. The first device includes: a first gate structure formed over an active region and a first air spacer disposed adjacent to the first gate structure. The second device includes: a second gate structure formed over an isolation structure and a second air spacer disposed adjacent to the second gate structure. The first air spacer and the second air spacer have different sizes.

A semiconductor device and a method of forming the same are provided. The method includes forming a sacrificial gate structure over an active region. A first spacer layer is formed along sidewalls and a top surface of the sacrificial gate structure. A first protection layer is formed over the first spacer layer. A second spacer layer is formed over the first protection layer. A third spacer layer is formed over the second spacer layer. The sacrificial gate structure is replaced with a replacement gate structure. The second spacer layer is removed to form an air gap between the first protection layer and the third spacer layer.

A method for fabricating a semiconductor device includes the steps of first forming a gate dielectric layer on a substrate, forming a gate material layer on the gate dielectric layer, patterning the gate material layer and the gate dielectric layer to form a gate structure, removing a portion of the gate dielectric layer, forming a spacer adjacent to the gate structure and at the same time forming an air gap between the gate dielectric layer and the spacer, and then forming a source/drain region adjacent to two sides of the spacer.

A semiconductor structure includes a first device and a second device. The first device includes: a first gate structure formed over an active region and a first air spacer disposed adjacent to the first gate structure. The second device includes: a second gate structure formed over an isolation structure and a second air spacer disposed adjacent to the second gate structure. The first air spacer and the second air spacer have different sizes.

A semiconductor device includes: a first electrode; a first semiconductor layer; a first insulating film extending downward from an upper surface of the first semiconductor layer, the first insulating film being columnar; a second electrode located in the first insulating film, the second electrode extending in a vertical direction, the second electrode being columnar; a second semiconductor layer partially provided in an upper layer portion of the first semiconductor layer, the second semiconductor layer being next to the first insulating film with the first semiconductor layer interposed; a third semiconductor layer partially provided in an upper layer portion of the second semiconductor layer; and a third electrode located higher than the upper surface of the first semiconductor layer, the third electrode overlapping a portion of the first insulating film, a portion of the first semiconductor layer, and a portion of the second semiconductor layer when viewed from above.

A dynamic random access memory includes a substrate, an isolation structure, and a buried word line structure. The isolation structure is located in the substrate and defines multiple active regions. The buried word line structure is located in a word line trench in the substrate, and the word line trench passes through the active regions and the isolation structure. The buried word line structure includes a gate conductive layer, a first gate dielectric layer, and a second gate dielectric layer. The gate conductive layer is located in the word line trench. The first gate dielectric layer is located on a sidewall and a bottom surface of the word line trench. The second gate dielectric layer is located between the first gate dielectric layer and the gate conductive layer, and a top surface of the second gate dielectric layer is lower than a top surface of the gate conductive layer.