A preparation method of an aluminum nitride (AlN) composite structure based on a two-dimensional (2D) crystal transition layer is provided. The preparation method includes: transferring the 2D crystal transition layer on a first periodic groove of an epitaxial substrate; forming a second periodic groove staggered with the first periodic groove on the 2D crystal transition layer; depositing a supporting protective layer; depositing a functional layer of a required AlN-based material; and removing the 2D crystal transition layer through thermal oxidation to obtain a semi-suspended AlN composite structure. The preparation method has low difficulty and is suitable for large-scale industrial production. Design windows of the periodic grooves and the AlN functional layer are large and can meet the material requirements of deep ultraviolet light-emitting diodes (DUV-LEDs) and radio frequency (RF) electronic devices for different purposes, resulting in a wide application range.

A semiconductor device includes channel structures spaced apart in a vertical direction; lower/upper first gate insulation patterns contacting lower/upper surfaces of the channel structures; a gate electrode surrounding lower/upper surfaces and a sidewall of the channel structures; and source/drain layers at sides of the gate electrode, wherein the channel structures include first/second 2D material layers stacked in the vertical direction, the first 2D material layer includes a semiconducting TMD including a first transition metal and first chalcogen elements that are bonded at lower/upper sides of the first transition metal, the second 2D material layer includes a second transition metal and a second chalcogen element, the second chalcogen element being bonded at a lower side of the second transition metal, and the second transition metal included in the second 2D material layer is covalently or ionically bonded with an element of the upper first gate insulation pattern.