Abstract: A capacitor structure includes a first comb-shaped electrode, a second comb-shaped electrode, a bottom electrode, an insulator layer, and a top electrode. The first comb-shaped electrode has a first pad and first fingers connecting to the first pad. The second comb-shaped electrode has a second pad and second fingers connecting to the first pad, wherein one of the second fingers is disposed between two adjacent first fingers. The bottom electrode includes a first portion, a second portion and a third portion which are spaced apart, wherein the first portion and the third portion are electrically coupled to the first comb-shaped electrode and the second comb-shaped electrode, respectively. The insulator layer is disposed over the bottom electrode. The top electrode is disposed over the insulator layer.

Abstract: A method for fabricating semiconductor device includes the steps of: providing a substrate having a first silicon layer, an insulating layer on the first silicon layer, and a second silicon layer on the insulating layer; forming a metal-oxide semiconductor (MOS) transistor on the substrate; forming an interlayer dielectric layer (ILD) on the MOS transistor; removing part of the ILD layer to form a first trench to expose the insulating layer; and performing a wet etching process through the first trench to remove part of the insulating layer for forming a first air gap under the MOS transistor.

Abstract: A method for fabricating semiconductor device includes the steps of: providing a substrate having a first silicon layer, an insulating layer on the first silicon layer, and a second silicon layer on the insulating layer; forming a metal-oxide semiconductor (MOS) transistor on the substrate; forming an interlayer dielectric layer (ILD) on the MOS transistor; removing part of the ILD layer to form a first trench to expose the insulating layer; and performing a wet etching process through the first trench to remove part of the insulating layer for forming a first air gap under the MOS transistor.