Method for forming self-align stop layer for borderless contact process

Abstract

A method for forming a self-align stop layer for borderless contact process is disclosed. In one embodiment, the present invention provides a semiconductor device which can simplify borderless contact fabrication, which includes providing a substrate incorporating a device. Sequentially, a pad oxide, a pad polysilicon, and a first dielectric layer are formed over the substrate. A first photoresist layer is formed over the first dielectric layer and then the first dielectric layer, the pad polysilicon, the pad oxide, and the substrate are etched using the photoresist layer as a mask to form an isolation inside said substrate. Consequentially, a second dielectric layer is deposited over the device and the isolation inside the substrate. The second dielectric layer is removed wherein the surface of the second dielectric layer is lower than the top surface of the substrate by a chemical mechanical polishing (CMP) and etching back. Next, a third dielectric layer is deposited over the device and within the isolation to form a self-align stop layer, wherein the third dielectric layer, the first dielectric layer, and a portion of the pad polysilicon layer are removed by a planarization process. Finally, said pad polysilicon layer and pad oxide layer are removed until a portion of the surface of said substrate is exposed, and then a gate oxide is formed over said substrate.