Patent attributes
The present invention provides a technology for forming the trenches having different depths in one semiconductor substrate, which enables easily conducting the photo resist process employed for the etch process and forming trenches at higher depth dimension accuracy. The openings of the first films are formed in the semiconductor substrate to expose surfaces of the semiconductor substrate, the semiconductor substrate is etched through the openings to a depth of the shallower trench and then the cell region is covered with the second photo resist pattern, and the peripheral region is etched through the first films to form the deeper trench. Since the etch process is conducted under the conditions, in which the surfaces of the semiconductor substrate are exposed (opened) within the openings in the first film, trenches having different depths can be formed with higher depth dimension accuracy by suitably controlling the etch conditions.
