Semiconductor memory device having composite dielectric film structure and methods of forming the same

A semiconductor device, comprising:

• a substrate including a memory region and a peripheral region;
• a plurality of memory cells located in the memory region;
• a plurality of transistors located in the peripheral region;
• and
• a composite dielectric film structure comprising at least two dielectric material layers extending over the plurality of transistors in the peripheral region, wherein a peripheral edge of the composite dielectric film structure is located within 300 nm of a boundary between the memory region and the peripheral region.

A method of fabricating a semiconductor device, comprising:

• forming a memory cell in a memory region of a substrate;
• forming a transistor including a metal gate in a peripheral region of the substrate;
• forming a composite dielectric film structure over the metal gate of the transistor in the peripheral region of the substrate, wherein the composite dielectric film structure comprises a first dielectric layer and a second dielectric layer over the first dielectric layer, and the second dielectric layer has a greater density than a density of the first dielectric layer;
• and
• performing a wet etch to remove a metal material from the semiconductor device, wherein the composite dielectric film structure protects the metal gate of the transistor in the peripheral region from being etched.