Bottom electrode of capacitor and fabricating method thereof

A bottom electrode of a capacitor and a method of fabrication is described. Hemispherical grained silicon (HSG) flexures are formed on a storage node to increase the effective area of the capacitor to increase the capacitance. The storage node includes a first region doped with phosphorous and a second undoped region. HSG flexures are formed on the surfaces of both the first and second region. Flexures formed on the first region are smaller in size than the flexures formed on the second region. This prevents adjacent storage nodes from becoming short-circuited with each other. Also, concave portions are formed on the second region between adjacent flexures. This further increases the effective surface area of the capacitor, which further increases the capacitance of the capacitor.