Semiconductor device structure including a tantalum pentoxide layer sandwiched between silicon nitride layers

An insulating structure includes a first silicon nitride layer, a tantalum pentoxide layer formed above the first silicon nitride (SiNx) layer, and a second silicon nitride layer formed above the tantalum pentoxide (Ta2O5) layer. The SiNx cladding layers prevent diffusion of the tantalum during heating. A high dielectric constant is provided. The thermal stability of the insulating structure is improved. The insulating structure may be included in a capacitor or a shallow trench isolation structure. An exemplary capacitor is formed with a substrate, a lower electrode, the three-layer SixNy/Ta2O5/SixNy structure and an upper electrode. The lower electrode may include a TiN layer formed over an aluminum layer, or a TiN layer formed over a polysilicon layer, or a polysilicon layer having an oxide barrier layer formed on it. The upper electrode may be a TiN layer or a polysilicon layer. An exemplary shallow trench isolation structure includes the SixNy/Ta2O5/SixNy structure as a liner on the sides and bottom of a shallow trench in the surface of a substrate. The shallow trench is filled with an oxide, such as TEOS. A variety of methods may be used for fabricating devices that include the SixNy/Ta2O5/SixNy structure.