METHOD OF FORMING SELF ALIGNED CONTACTS IN SEMICONDUCTOR DEVICE

摘要

PURPOSE: A method for providing SAC(Self-Aligned contact) is provided to be capable of providing a flat surface for all critical exposure of photoresist masks. CONSTITUTION: A trench is formed in a substrate through a mask of a silicon nitride deposited on an oxide layer(501). A gate oxide layer is formed on the walls of the trenches(503). A polysilicon layer is filled in the trenches(505). The excess of polysilicon is removed from the surface of the silicon nitride mask by CMP(507). A photoresist mask is covered on a location of a gate bus(509). A recess is formed above the polysilicon plugs(511). An insulator is filled in the recess(513). By using a fourth photo resist mask, a contact window is defined to open the nitride layer(515). The silicon nitride film is selectively etched(517). Moreover, electric contact trenches are defined using self-aligned spacer operations(519), and a fifth photo resist mask is applied to pattern metal contacts(521). A flat surface is provided for all critical exposure of the photo resist masks.