A semiconductor device according to the present disclosure includes a first transistor and a second transistor disposed over the first transistor. The first transistor includes a plurality of channel members vertically stacked over one another, and a first source/drain feature adjoining the plurality of channel members. The second transistor includes a fin structure, and a second source/drain feature adjoining the fin structure. The semiconductor device further includes a conductive feature electrically connecting the first source/drain feature and the second source/drain feature.

A second gate electrode is adjacent, in a Y direction, to a first tip of a semiconductor layer in a first active region such that a protruding distance of a second tip of the second gate electrode protruded, in a X direction, from the semiconductor layer in the first active region is greater than or equal to 0. Also, the first tip of the semiconductor layer in the first active region is covered with a second sidewall spacer. Further, a first epitaxial layer and the second gate electrode are electrically connected to each other via a first shared contact plug formed so as to across the first epitaxial layer, the second sidewall spacer and the second gate electrode.

A Group-III element nitride semiconductor substrate includes: a first surface; and a second surface. The Group-III element nitride semiconductor substrate has a c-plane tilted with respect to a direction of the first surface, and a direction of the tilt falls between a <1-100> direction and a <11-20> direction.

A method of performing heteroepitaxy comprises exposing a substrate to a carrier gas, a first precursor gas, a Group II/III element, and a second precursor gas, to form a heteroepitaxial growth of one of GaAs, AlAs, InAs, GaP, InP, ZnSe, GaSe, CdSe, InSe, ZnTe, CdTe, GaTe, HgTe, GaSb, InSb, AlSb, CdS, GaN, and AlN on the substrate; wherein the substrate comprises one of GaAs, AlAs, InAs, GaP, InP, ZnSe, GaSe, CdSe, InSe, ZnTe, CdTe, GaTe, HgTe, GaSb, InSb, AlSb, CdS, GaN, and AlN; wherein the carrier gas is Hz, wherein the first precursor is HCl, the Group II/III element comprises at least one of Zn, Cd, Hg, Al, Ga, and In; and wherein the second precursor is one of AsH.sub.3 (arsine), PH.sub.3 (phosphine), H.sub.2Se (hydrogen selenide), H.sub.2Te (hydrogen telluride), SbH.sub.3 (hydrogen antimonide), H.sub.2S (hydrogen sulfide), and NH.sub.3 (ammonia). The process may be an HVPE (hydride vapor phase epitaxy) process.

A method of manufacturing a PN junction includes successive steps for: forming at least one trench in a semiconductor substrate of a first conductivity type; and filling the at least one trench with a semiconductor material of a second conductivity type, different from the first conductivity type.

A method includes forming a first fin-group having has a plurality of semiconductor fins, and a second fin-group. The plurality of semiconductor fins include a first semiconductor fin, which is farthest from the second fin-group among the first fin-group, a second semiconductor fin, and a third semiconductor fin, which is closest to the second fin-group among the first fin-group. The method further includes performing an epitaxy process to form an epitaxy region based on the plurality of semiconductor fins. The epitaxy region includes a first portion and a second portion. The first portion is in middle between the first semiconductor fin and the second semiconductor fin. The first portion has a first top surface. The second portion is in middle between the second semiconductor fin and the third semiconductor fin. The second portion has a second top surface lower than the first top surface.

The present disclosure describes epitaxial oxide high electron mobility transistors (HEMTs). In some embodiments, a HEMT comprises: a substrate; a template layer on the substrate; a first epitaxial semiconductor layer on the template layer; and a second epitaxial semiconductor layer on the first epitaxial semiconductor layer. The template layer can comprise crystalline metallic Al(111). The first epitaxial semiconductor layer can comprise (Al.sub.xGa.sub.1-x).sub.yO.sub.z, wherein 0≤x≤1, 1≤y≤3, and 2≤z≤4, wherein the (Al.sub.xGa.sub.1-x).sub.yO.sub.z comprises a Pna21 space group, and wherein the (Al.sub.xGa.sub.1-x)O.sub.z comprises a first conductivity type formed via polarization. The second epitaxial semiconductor layer can comprise a second oxide material.

The present disclosure describes methods and epitaxial oxide devices with impact ionization. A method can comprise: applying a bias across a semiconductor structure using a first electrical contact and a second electrical contact; injecting a hot electron, from the first electrical contact, through a second semiconductor layer, and into a conduction band of a first epitaxial oxide material; and forming an excess electron-hole pair in an impact ionization region of the first semiconductor layer via impact ionization. The semiconductor structure can comprise: the first electrical contact; the first semiconductor layer with the first epitaxial oxide material with a first bandgap coupled to the first electrical contact; a second semiconductor layer with a second epitaxial oxide material with a second bandgap coupled to the first semiconductor layer; and a second electrical contact coupled to the second semiconductor layer, wherein the second bandgap is wider than the first bandgap.

The present disclosure provides techniques for epitaxial oxide materials, structures and devices. In some embodiments, a semiconductor structure includes an epitaxial oxide heterostructure, including: a substrate; a first epitaxial oxide layer comprising (Ni.sub.x1Mg.sub.y1Zn.sub.1-x1-y1)(Al.sub.q1Ga.sub.1-q1).sub.2O.sub.4 wherein 0≤x1≤1, 0≤y1≤1 and 0≤q1≤1; and a second epitaxial oxide layer comprising (Ni.sub.x2Mg.sub.y2Zn.sub.1-x2-y2)(Al.sub.q2Ga.sub.1-q2).sub.2O.sub.4 wherein 0≤x2≤1, 0≤y2≤1 and 0≤q2≤1. In some cases, at least one condition selected from x1≠x2, y1≠y2, and q1≠q2 is satisfied.

The present disclosure describes epitaxial oxide devices with impact ionization. In some embodiments, a semiconductor device comprises: a first semiconductor layer; a second semiconductor layer coupled to the first semiconductor layer; and a first and a second electrical contact coupled to the second and first semiconductor layers, respectively. The first semiconductor layer can comprise a first epitaxial oxide material with a first bandgap and an impact ionization region. The second semiconductor layer can comprise a second epitaxial oxide material with a second bandgap that is wider than the first bandgap.