| 摘要 |
PURPOSE:To obtain a stabilized overvoltage protective device by a method wherein a pair of discharge electrodes of polycrystalline or amorphous Si or low melting point metal are arranged at the prescribed interval, and they are operated at the desired voltage using the vacant space closed by an interelectrode region and an insulating film. CONSTITUTION:An etching is performed on the SiO2 film 2 located on an Si substrate 1 using a reactive ion, and concavities 3 and 3' are provided accurately with the corner of a concavity 21 formed at a right angle. A poly Si layer 22 is selectively formed striding over a barrier 21, and P or As is doped. Then, the above is covered by a PSG5, and a laser beam 23 is irradiated. As the PSG5 is transparent to a laser beam, it is absorbed into the poly Si 22, the layer 22 is rapidly heated up and fused, the upper layer part of the layer 22 located above the barrier 21 is fused and flowed away and the layer 22 is divided into layers 4 and 4'. The PSG 5 and the SiO2 film 2 are hardly heated up while the above procedures are being performed and they can maintain their original form, thereby enabling to form a cavity 6 in the short time of a millisecond or less. As the operating voltage can be optionally established taking the quality of material of the electrodes, the interval between the electrodes and the like into consideration, an overvoltage protective device which is operated stably can be obtained. |
