Patent ID: 6955957
Filing Date: 2005-10-18
Classification: H01L

Abstract:
1. A method of forming a floating gate in a flash memory device, comprising the steps of: (a) forming a gate oxide film on a semiconductor substrate; (b) depositing a first polysilicon film on the gate oxide film; (c) etching portions of the first polysilicon film, the gate oxide film and the semiconductor substrate to form a trench; (d) depositing an oxide film for an isolation film on the entire top surface so that the trench is gap-filled and then implementing a polishing process; (e) implementing an etch process using a dry etch method to etch the oxide film for the isolation film, thus forming the oxide film having a protrusion of a vertical nipple shape; and (f) depositing a second polysilicon film on the entire top surface and then implementing a polishing process until a top surface of the protrusion is exposed so that a floating gate which consists of the first and the second polysilicon film is formed; and (g) implementing a pre-treatment cleaning process to form the top surface of the protrusion into a semicircle shape.