Process of producing a semiconductor device

A process of producing a semiconductor device for a liquid crystal display device which comprises:

• a display portion having a plurality of pixels and a thin film transistor comprising respective non-monocrystalline semiconductor active region connected to each said pixel;
• a peripheral circuit driving portion comprising a monocrystalline semiconductor region for receiving image input signals and driving said display portion, wherein said display portion and said peripheral circuit driving portion are monolithically formed;
• a first oxide film under said non-monocrystalline semiconductor region;
• and
• a second oxide film which is formed in said peripheral circuit driving portion and isolates an element constituting said peripheral circuit driving portion:
• wherein said first oxide film and said second oxide film are formed to be continuous over at least part of the boundary between said display portion and said peripheral circuit portion, the height of said first oxide film in an upper surface level being higher than that of said second oxide film or the height of said second oxide film in a low surface level being higher than that of said first oxide film.