| 摘要 |
PURPOSE: To provide the insulation method of a semiconductor element which is capable of improving insulation characteristic between a semiconductor unit element and a semiconductor substrate, reducing an area required for the insulation between a unit element and preventing a latch-up phenomenon between the unit element. CONSTITUTION: This method is provided with a process for forming a semiconductor substrate 20, composed of the three-layer cross sectional structure of an upper conductive layer 22, a high concentration impurity layer and a lower conductive layer 23, the process for executing a photoetching process to the upper conductive layer 22, removing the upper conductive layer 22 present at the part of an element isolation region and forming an opening reaching to the high concentration impurity layer, the process for performing immersion in an HF solution of a prescribed concentration, executing an anode reaction processing and selectively converting only the high concentration impurity layer to a porous silicon layer, and the process for executing wet oxidation and converting the porous silicon layer into a buried oxide layer 21-2.
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