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Abstract

The present invention provides a method of manufacturing a nonvolatile semiconductor memory device. In the method of the present invention. Arsenic ions are implanted into an element region of a silicon substrate so as to form a first impurity region. Then, an insulating film is formed on the silicon substrate in the element region, followed by forming a heat resistant film on the entire surface of the silicon substrate. Further, a resist film is formed on the silicon substrate, followed by patterning the resist film to form an opening on at least the first impurity region. After the patterning step, the heat resistant film positioned below the opening of the resist film is removed, followed by implanting phosphorus ions into the substrate using the patterned resist film as a mask so as to form a second impurity region. In the next step, the resist film is removed and, then, annealing is applied with the heat resistant film used as a mask. After the annealing step, the resist film is removed, and an annealing is performed with the heat resistant film used as a mask, followed by removing the insulating film using the heat resistant film as a mask. Finally, a tunnel oxide film is formed on that portion of the silicon substrate, followed by forming an electrode on the tunnel oxide film so as to manufacture a desired nonvolatile semiconductor memory device.

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First Claim