| 摘要 |
A method of the invention comprises the step of forming on part of a silicon substrate (101) a three-layered film consisting of a first silicon nitride film (102), a first silicon oxide film (103) and a second silicon nitride film (104) and forming a third silicon nitride film (106) on side wall portions of the three-layered film, the step of etchiing an exposed silicon substrate (101) to form a first groove having substantially vertical side walls and refilling the first groove with a silicon oxide film (108), and the step of removing the second and third silicon nitride films (104,106) to form a second groove (111) having substantially vertical side walls relative to the silicon substrate (101) exposed by the removal. Accordingly, the second groove (111) which serves as a trench groove by self alignment is formed an end portion of the silicon oxide film (108) within a field region (107) as having a structure which is in direct contact with an element forming region (115). In addition, the groove width is constant as a width of the third silicon nitride film (106), thus permitting the parasitic capacitance between the collector and the substrate to be minimized.
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