so as to have a width substantially equal to the minimum aperture width since there is substantially no side etching effect thus it is possible to form an opening having a size within a resist aperture limit of about 1 u03bcm by performing dry etching in accordance with this embodiment 1 the second embodiment of the present invention i e embodiment 2 will be described in this embodiment a gaa transistor is formed without using opening 4 of the first embodiment fig6 a through 6c and fig7 a through 7c are diagrams showing the structure of a semiconductor device in accordance with this embodiment and a method of manufacturing the semiconductor device the process step shown in fig7 a follows the process step shown in fig6 c in this embodiment a silicon nitride film 9 is formed on first silicon oxide film 2 to provide a space 10 between first silicon oxide film 2 and channel silicon film 3 silicon substrate 1 first silicon oxide film 2 channel silicon film 3 second silicon oxide film 5 and gate electrode 6 are the same as those of the first embodiment and will not be specifically described fig8 a through 8e are each a cross sectional view taken along a line corresponding to the line 8 8 of fig6 c or 7c fig8 a 8b 8c and 8d are cross sectional views of fig6 a fig6 b fig6 c and fig7 a respectively and fig8 e is a cross sectional view of fig7 b and 7c fig9 is a cross sectional view taken along the line 9 9 of fig7 c the method of manufacturing the semiconductor device of this embodiment will now be.