本发明提出一种半导体设备及其制造方法，即使高度积体化，亦能够防止渠沟隔离绝缘膜之隔离特性的劣化、防止掺杂剂扩散层之接触电阻或接点漏电的增加、且不会使制程更为复杂。包含下列步骤:形成第一至第三防护膜以覆盖硅基材的主要表面上之渠沟隔离绝缘膜及MOS晶体管;于防护膜上形成一具有蚀刻选择性之层间绝缘膜;及以高于防护膜之蚀刻速率对层间绝缘膜进行蚀刻以开通一接触孔。在蚀刻过程中，被防护膜所覆盖之渠沟隔离绝缘膜并未受到蚀刻，因而隔离特性不会劣化。防护膜能够防止渠沟隔离绝缘膜表面的蚀刻，并防止掺杂剂扩散层之接触电阻的增加以及接点漏电，同时，即使用来开通接触孔之遮罩的开口窗大于掺杂剂扩散层的表面区域，借由自我定位，可以开通一微小开口尺寸的接触孔。

This invention provides a semiconductor device which can prevent deterioration of separation properties in a trench separation insulating film, can prevent increase of a contact resistance and junction leak in a dopant diffusion layer, and does not make its manufacturing process complicated, while being highly integrated, and a manufacturing process therefor. The process comprises forming from first to third protective films which cover a trench separation insulating film and an MOS transistor formed on a main surface of a silicon substrate; forming an interlayer insulating film having an etching selectivity on the protective films; and etching the interlayer insulating film in a higher etching rate than that for the protective films, to open a contact hole. During the etching process, the trench separation insulating film covered by the protective films is not etched, so that separation properties are not deteriorated. The protective films may prevent etching of the surface of the trench separation insulating film and prevent increase of a contact resistance and junction leak, as well as allows a fine opening size of contact hole to be opened by self-alignment even when an opening window of a mask for opening a contact hole is larger than the surface area of the dopant diffusion layer.