METHOD FOR FORMING SOI SUBSTRATE FOR SEMICONDUCTOR

PURPOSE: A method for forming an SOI(silicon-on-insulator) substrate for a semiconductor is provided to use a relatively inexpensive silicon substrate and control a soft error and a latch-up by forming an SOI substrate during a process for forming an STI(shallow trench isolation) while using porous silicon. CONSTITUTION: After an isolation trench is formed on a silicon substrate(101) on which an SOI structure is to be formed, an insulation layer is formed on the resultant structure. The insulation layer is formed on the bottom of the trench except the sidewall region of the trench to expose the silicon substrate. An oxide process is performed through the trench to which the silicon substrate is exposed so that a predetermined height of the silicon substrate not higher than the bottom of the trench is formed of an SOI layer(107) for the SOI structure. A trench filling material is deposited on the resultant structure to form a trench isolation layer.