The present disclosure describes a method includes forming a fin structure including a fin base portion and a stacked fin portion on a substrate. The stacked fin portion includes a first semiconductor layer on the fin base portion, a second semiconductor layer above the first semiconductor layer, and a sacrificial semiconductor layer between the first and second semiconductor layers. The method further includes replacing the sacrificial semiconductor layer with a negative capacitance (NC) layer and forming gate electrodes around the NC layer, the first semiconductor layer, and the second semiconductor layer. The NC layer includes an NC dielectric material.

A gate all around transistor may be improved to provide better transistor circuits performance. In one example, a transistor circuit may include a dielectric or air gap as an insulator between the channels of the transistors in the circuit. In another example, a transistor may include a first channel surrounded by a first metal, a second channel surrounded by a second metal proximate to the first channel, and an insulator, such as a dielectric or air gap, between the first metal and the second metal. The insulator helps reduce the parasitic capacitance between the source/drain regions and the metal fill regions of the transistor.

A 3D semiconductor device, the device including: a first level including single crystal first transistors, and a first metal layer, where the first level is overlaid by a first isolation layer; a second level including second transistors, where the first isolation layer is overlaid by the second level, and where the second level is overlaid by a second isolation layer; a third level including single crystal third transistors, where the second isolation layer is overlaid by the third level, where the third level is overlaid by a third isolation layer, where the third level is bonded to the second isolation layer, and where the bonded includes at least one oxide to oxide bond.

A transistor is disclosed. In an embodiment a transistor includes a first semiconductor region of a substrate, a first trench delimiting the first semiconductor region on a first side, a first electrically-conductive element located in the first trench, a channel area in contact with the first semiconductor region and a first area of contact with the first semiconductor region, wherein the channel area and the first area of contact are on the same surface side of the substrate.

A 3D semiconductor device, the device including: a first level including a plurality of first metal layers; a second level, where the second level overlays the first level, where the second level includes at least one single crystal silicon layer, where the second level includes a plurality of transistors, where each transistor of the plurality of transistors includes a single crystal channel, where the second level includes a plurality of second metal layers, where the plurality of second metal layers include interconnections between the transistors of the plurality of transistors, where the second level is overlaid by a first isolation layer; and a connective path between the plurality of transistors and the plurality of first metal layers, where the connective path includes a via disposed through at least the single crystal silicon layer, and where at least one of the plurality of transistors includes a gate all around structure.

A 3D semiconductor device, the device including: a first level including a plurality of first metal layers; a second level, where the second level overlays the first level, where the second level includes at least one single crystal silicon layer, where the second level includes a plurality of transistors, where each transistor of the plurality of transistors includes a single crystal channel, where the second level includes a plurality of second metal layers, where the plurality of second metal layers include interconnections between the transistors of the plurality of transistors, and where the second level is overlaid by a first isolation layer; and a connective path between the plurality of transistors and the plurality of first metal layers, where the connective path includes a via disposed through at least the single crystal silicon layer, and where at least one of the transistors includes a four sided gate.

A semiconductor device is provided. The semiconductor device includes a first stacked structure including a plurality of first insulating patterns and a plurality of first semiconductor patterns alternately stacked on a substrate, the first stacked structure extending in a first direction parallel to an upper surface of the substrate, a first conductive pattern on one side surface of the first stacked structure, the first conductive pattern extending in a second direction crossing the upper surface of the substrate, and a first ferroelectric layer between the first stacked structure and the first conductive pattern, the first ferroelectric layer extending in the second direction, wherein each of the first semiconductor patterns includes a first impurity region, a first channel region and a second impurity region which are sequentially arranged along the first direction.

A 3D semiconductor device, the device including: a first level including a plurality of first metal layers; a second level, where the second level overlays the first level, where the second level includes at least one single crystal silicon layer, where the second level includes a plurality of transistors, where each transistor of the plurality of transistors includes a single crystal channel, where the second level includes a plurality of second metal layers, where the plurality of second metal layers include interconnections between the transistors of the plurality of transistors, and where the second level is overlaid by a first isolation layer; and a connective path from the plurality of transistors to the plurality of first metal layers, where the connective path includes a via disposed through at least the single crystal silicon layer, and where at least one of the via includes a contact to at least one of the transistors.

The present disclosure describes a method includes forming a fin structure including a fin base portion and a stacked fin portion on a substrate. The stacked fin portion includes a first semiconductor layer on the fin base portion, a second semiconductor layer above the first semiconductor layer, and a sacrificial semiconductor layer between the first and second semiconductor layers. The method further includes replacing the sacrificial semiconductor layer with a negative capacitance (NC) layer and forming gate electrodes around the NC layer, the first semiconductor layer, and the second semiconductor layer. The NC layer includes an NC dielectric material.

The present application discloses a method for fabricating a semiconductor device with a flat surface. The method for fabricating a semiconductor device including providing a substrate, forming a gate structure on the substrate, and forming a plurality of word lines having top surfaces at a same vertical level as a top surface of the gate structure.