Method of manufacturing floating gate type transistor

Abstract

A semiconductor device includes a field oxide film, a plurality of word lines, an insulating interlayer film, a plurality of contact holes, a plurality of protective diffusion layers, a plurality of common contact holes, and a plurality of metal plugs. The field oxide film is formed on a silicon substrate having one conductivity type. The word lines are formed by patterning on the field oxide film. The insulating interlayer film is formed on the field oxide film to cover the word lines. The contact holes are formed in the field oxide film to be self-aligned with the word lines. The protective diffusion layers have an opposite conductivity type and are formed on a surface of the semiconductor substrate to correspond to the contact holes. The common contact holes are formed in the insulating interlayer film to extend across the word lines and the protective diffusion layers. The common contact holes are formed at a depth to reach the protective diffusion layers while partly exposing the word lines. The metal plugs fill the common contact holes to electrically connect the protective diffusion layers and the word lines with each other. A method of manufacturing a semiconductor device is also disclosed.