Method to combine high voltage device and salicide process

Abstract

A method for integrating salicide and high voltage device processes in the fabrication of high and low voltage devices on a single wafer is described. Isolation areas are formed on a semiconductor substrate surrounding and electrically isolating a low voltage device area from a high voltage device area. A gate oxide layer is grown in the device areas. A polysilicon layer is deposited overlying the gate oxide layer and isolation areas. A first photomask is formed over a portion of the high voltage device area wherein the first photomask also completely covers the low voltage device area. The polysilicon layer is etched away where it is not covered by the photomask to form a high voltage device. Ions are implanted to form lightly doped source and drain regions within the semiconductor substrate adjacent to the high voltage device wherein the first photomask protects the polysilicon layer in the low voltage device area from the ions. The first photomask is removed. A second photomask is formed over a portion of the low voltage device area where a gate electrode is to be formed wherein the second photomask also completely covers the high voltage device area. The polysilicon layer not covered by the second photomask is etched away to form the gate electrode. The second photomask is removed. The low voltage and high voltage area devices are silicided and the fabrication of the integrated circuit device is completed.