Disclosed herein are field-effect transistors with asymmetric gate stacks. An example transistor includes a channel material and an asymmetric gate stack, provided over a portion of the channel material between source and drain (S/D) regions. The gate stack is asymmetric in that a thickness of a gate dielectric of a portion of the gate stack closer to one of the S/D regions is different from that of a portion of the gate stack closer to the other S/D region, and in that a work function (WF) material of a portion of the gate stack closer to one of the S/D regions is different from a WF material of a portion of the gate stack closer to the other S/D region. Transistors as described herein exploit asymmetry in the gate stacks to improve the transistor performance in terms of high breakdown voltage, high gain, and/or high output resistance.

The present disclosure teaches semiconductor devices and methods for manufacturing the same. Implementations of the semiconductor device may include: a semiconductor substrate; a semiconductor fin positioned on the semiconductor substrate; and a gate structure positioned on the semiconductor fin, where the gate structure includes a gate dielectric layer on a part of a surface of the semiconductor fin and a gate on the gate dielectric layer; where the gate includes a metal gate layer on the gate dielectric layer and a semiconductor layer on a side surface of at least one side of the metal gate layer; and where the semiconductor layer includes a dopant, where a conductivity type of the dopant is the opposite of a conductivity type of the semiconductor fin. The present disclosure can improve a work function of the device, thereby improving a current characteristic of the device during a working process, reducing the short channel effect (SCE), and lowering a leakage current.

A semiconductor structure includes a metal gate structure (MG) formed over a substrate, a first gate spacer formed on a first sidewall of the MG, a second gate spacer formed on a second sidewall of the MG opposite to the first sidewall, where the second gate spacer is shorter than the first gate spacer, a source/drain (S/D) contact (MD) adjacent to the MG, where a sidewall of the MD is defined by the second gate spacer, and a contact feature configured to electrically connect the MG to the MD.

A MOSFET fabricated in a semiconductor substrate, includes: a gate oxide region formed atop the semiconductor substrate; a gate polysilicon region formed on the gate oxide region; a source region of a first doping type formed in the semiconductor substrate and located at a first side of the gate polysilicon region; and a drain region of the first doping type formed in the semiconductor substrate and located at a second side of the gate polysilicon region. The gate polysilicon region has a first sub-region of the first doping type, a second sub-region of the first doping type, and a third sub-region of a second doping type, wherein the first sub-region is laterally adjacent to the source region, the second sub-region is laterally adjacent to the drain region, and the third sub-region is formed laterally between the first and second sub-regions.

A method to form a transistor device with a recessed gate structure is provided. In one embodiment, a gate structure is formed overlying a device region and an isolation structure. The gate structure separates a device doping well along a first direction with a pair of recess regions disposed on opposite sides of the device region in a second direction perpendicular to the first direction. A pair of source/drain regions in is formed the device region on opposite sides of the gate structure. A sidewall spacer is formed extending along sidewalls of the gate structure, where a top surface of the sidewall spacer is substantially flush with the top surface of the gate structure. A resistive protection layer is then formed on the sidewall spacer and covering the pair of recess regions.

The present disclosure provides a method for preparing a semiconductor memory device with air gaps between conductive features. The method includes forming an isolation layer defining a first active region in a substrate; forming a first doped region in the first active region; forming a first word line buried in a first trench adjacent to the first doped region; and forming a high-level bit line contact positioned on the first doped region; forming a first air gap surrounding the high-level bit line contact. The forming of the first word line comprises: forming a lower electrode structure and an upper electrode structure on the lower electrode structure. The forming of the upper electrode structure comprises: forming a source layer substantially covering a sidewall of the first trench; forming a conductive layer on the source layer; and forming a work-function adjustment layer disposed between the source layer and the conductive layer.

The present disclosure provides a semiconductor device and a manufacturing method thereof, and an electronic device including the semiconductor device. The semiconductor device includes: a substrate; an active region including a first source/drain region, a channel region and a second source/drain region stacked sequentially on the substrate and adjacent to each other; a gate stack formed around an outer periphery of the channel region; and spacers formed around the outer periphery of the channel region, respectively between the gate stack and the first source/drain region and between the gate stack and the second source/drain region; wherein the spacers each have a thickness varying in a direction parallel to a top surface of the substrate.

The present disclosure describes semiconductor structure and a method for forming the same. The semiconductor structure can include a substrate and a gate structure over the substrate, where the gate structure can include two opposing spacers, a dielectric layer formed on side surfaces of the two opposing spacers, and a gate metal stack formed over the dielectric layer. A top surface of the gate metal stack can be below a top surface of the dielectric layer. An example benefit of the semiconductor structure is to improve structure integrity of tight-pitch transistors in integrated circuits.

A semiconductor structure includes a metal gate structure (MG) formed over a substrate, a first gate spacer formed on a first sidewall of the MG, a second gate spacer formed on a second sidewall of the MG opposite to the first sidewall, where the second gate spacer is shorter than the first gate spacer, a source/drain (S/D) contact (MD) adjacent to the MG, where a sidewall of the MD is defined by the second gate spacer, and a contact feature configured to electrically connect the MG to the MD.

Semiconductor device having less defects in a gate insulating film and improved reliability and methods of forming the semiconductor devices are provided. The semiconductor devices may include a gate insulating film on a substrate and a gate electrode structure on the gate insulating film. The gate electrode structure may include a lower conductive film, a silicon oxide film, and an upper conductive film sequentially stacked on the gate insulating film. The lower conductive film may include a barrier metal layer.