Patent ID: 7205208

Claim:
A method of manufacturing a semiconductor device, comprising: forming a first trench in a first region of a substrate and a second trench in a second region of the substrate different from the first region, the first trench being shallower than the second trench; forming an insulation layer in the second trench, so that semiconductor structures formed in the first trench are electrically isolated; and forming a conductive layer filling the first trench and extending above the first trench, wherein forming the insulation layer includes: sequentially forming an oxide layer and a nitride layer along sidewalls and bottoms of the first and second trenches and on a surface of the first region; filling the first and second trenches with an insulation material to thereby form an insulation layer on the substrate such that the insulation layer includes a void in the first trench; polishing the insulation layer until a top surface of the nitride layer is exposed in the first region, so that a portion of the first trench is exposed corresponding to the void; and removing the insulation layer in the first trench.