| 摘要 |
PURPOSE: A fabrication method of a semiconductor device is provided to improve punch through characteristics by forming a dual isolation layer. CONSTITUTION: In the method, a pad oxide layer(42) and a pad nitride layer(43) are sequentially deposited on a semiconductor substrate(41) and then selectively etched to expose a portion of the substrate(41). Next, a nitride layer is formed over a resultant structure and then etched to form the first spacer(44) on sides of the pad layers(42,43). Next, the first isolation layer is formed on a resultantly exposed portion of the substrate(41) by thermal oxidation and then removed. Next, the second spacer(46) is formed on a side of the first spacer(44), and then the second isolation layer(47) is formed on a resultantly exposed portion of the substrate(41). Next, the first and second spacers(44,46) and the pad layers(42,43) are wholly removed, and then necessary impurities are implanted into the substrate(41). Since the second isolation layer(47) has a greater depth and a smaller width than the first isolation layer has, an effective distance between a heavily doped region and a well is increased and thereby punch through characteristics are improved.
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