| 摘要 |
<p>PURPOSE:To improve storage maintaining characteristics, by a method wherein oxide films on side surfaces of floating electrodes are formed by respectively performing thermal oxidizing before and after ion implantation process to form a source region and a drain region. CONSTITUTION:On a semiconductor substrate 1 surface defined by a field insulating film 2, the following are formed in order; a first gate insulating film 3, a first polycrystalline silicon film 4, a second gate insulating film 5 and a second polycrystalline silicon film 6. By selective etching, a control gate electrode 6' composed of a silicon film 6, and a floating gate electrode 4' composed of a silicon film 4 are formed. By thermal oxidizing, side surface oxide films 8 are formed on the side surfaces of the electrodes 6 ' and 4'. By using the electrode 6', the oxide film 8 and the insulating film 2 as masks, and performing ion implantation, a source region 10 and a drain region 9 are formed. By performing thermal oxidizing again, the oxide film 8 is thickened. As a result, storage maintaining characteristics are improved.</p> |
