A semiconductor structure includes a substrate having first and second bottom electrodes disposed thereon. The first bottom electrode includes a first sidewall and a second sidewall. An upper portion of the first sidewall comprises a slope profile. The second bottom electrode includes a third sidewall and a fourth sidewall. The second sidewall is opposite to the third sidewall. An upper supporting layer extends laterally between and the first bottom electrode and the second bottom electrode and directly contacts the second sidewall and the third sidewall. A lower end of the slope profile is not lower than a lower surface of the upper supporting layer. A cavity extends laterally between the substrate and the upper supporting layer. A capacitor dielectric layer is formed along the first bottom electrode and the second bottom electrode. A conductive material is formed on the capacitor dielectric layer and fills the cavity.