METHOD FOR MANUFACTURING SEMICONDUCTOR MEMORY DEVICE

摘要

PURPOSE: A method for manufacturing a semiconductor memory device is provided to simplify a trench forming process by forming simultaneously trenches with different depths at a cell region and a peripheral region. CONSTITUTION: The first multilayer dielectric is on a semiconductor substrate(10) of a cell region(11). The first multilayer dielectric includes the first oxide layer(13), a nitride layer(15) and the second oxide layer(17). The second multilayer dielectric is on the substrate of a peripheral region(12). The second multilayer dielectric includes the first oxide layer and the nitride layer. The substrate is partially exposed at the cell and peripheral region by forming the first and second opening portion through the first and second multilayer dielectric. The second opening portion is prolonged into the substrate as much as a predetermined depth due to the thickness of the second multilayer dielectric. The first and second trench(19a,19b) are formed under the first and second opening portion by using a photolithography. The first depth(D1) of the first trench is smaller than the second depth(D2) of the second trench as much as the predetermined depth.