Mask ROM, method for fabricating the same, and method for coding the same

1. A method for fabricating a mask ROM comprising:

depositing an insulating film on a semiconductor substrate having a device isolation region and an active region;

forming BN junction regions by implanting impurity ions to predetermined portions of the substrate, wherein forming the BN junction regions comprises:

depositing a nitride film on the insulating film;

forming nitride film patterns by selectively removing the nitride film;

forming first sidewall spacers at sides of the nitride film patterns;

implanting impurity ions into the semiconductor substrate using the nitride film patterns and the first sidewall spacers as masks to form the BN junction regions; and

removing the nitride film patterns and the spacers;

forming first electrode layers by depositing polysilicon on the insulating film and selectively removing the polysilicon;

forming second sidewall spacers at sides of the first electrode layers; and

forming second electrode layers between the second sidewall spacers.

2. The method of claim 1 , wherein the spacers are formed by an etch-back process after the insulating film is deposited on an entire surface of the semiconductor substrate including the first electrode layers.

3. The method of claim 1 , wherein the second electrode layers have a height equal to that of the first electrode layers.