Patent ID: 7709346

Claim:
A method of manufacturing a semiconductor device, the method comprising: forming a plurality of gate trenches in a semiconductor substrate to extend in a first direction; forming a sacrificial layer over the plurality of gate trenches such that the plurality of gate trenches is filled; forming isolation trenches in the semiconductor substrate after forming the plurality of gate trenches and forming the sacrificial layer, the isolation trenches defining a plurality of active regions that extend in a second direction that is perpendicular to the first direction; forming an isolation layer by filling the isolation trenches with an insulating material, the isolation layer defining the active regions; exposing gate regions in the active regions by completely removing the sacrificial layer from the gate trenches; forming a gate insulating layer in the gate regions; and forming a plurality of gate electrodes over the gate insulating layer, each of the plurality of gate electrode being formed in a corresponding gate trench.