A memory cell with hard mask insulator and its manufacturing methods are provided. In some embodiments, a memory cell stack is formed over a substrate having a bottom electrode layer, a resistance switching dielectric layer over the bottom electrode layer, and a top electrode layer over the resistance switching dielectric layer. A first insulating layer is formed over the top electrode layer. A first metal hard masking layer is formed over the first insulating layer. Then, a series of etch is performed to pattern the first metal hard masking layer, the first insulating layer, the top electrode layer and the resistance switching dielectric layer to form a first metal hard mask, a hard mask insulator, a top electrode, and a resistance switching dielectric.