Patent ID: 8685831

Claim:
A method of forming a semiconductor device, comprising the steps of: forming a first pattern containing an opening for a deep isolation trench on a substrate of said semiconductor device; forming a first shallower portion of said deep isolation trench; forming dielectric sidewalls on walls of said first shallower portion; etching said substrate below said first shallower portion to form a second deeper portion of said deep isolation trench; filling said deep isolation trench with a dielectric fill material; forming a second photoresist pattern with openings for a shallow isolation trench on said substrate prior to said step of etching said substrate below said first shallower portion to form a second deeper portion of said deep isolation trench; etching said second photoresist pattern into a hardmask on said substrate; removing said second photoresist pattern; etching said shallow trench isolation trench at the same time said second deeper portion of said deep isolation trench is etched; and filling said shallow isolation trench with said dielectric fill material at the same time as filling said deep isolation trench with a dielectric fill material.