Manufacturing method of semiconductor device

A method of manufacturing a semiconductor device, the method comprising:

• forming first trenches and second trenches at the same time, wherein the first trenches are formed in a peripheral region of a substrate, wherein the substrate includes a memory array region and the peripheral region, wherein the second trenches define an active region, and wherein the first trenches are provided between the second trenches;
• forming offset insulating layers in the first trenches and isolation layers in the second trenches;
• and
• forming a gate electrode in the active region between the offset insulating layers, wherein the gate electrode has edges overlapping with the offset insulating layers.