PURPOSE: To obtain the titled device of high integration degree and high speed by endowing a partial circuit that requires high withstand voltage with this quality by a method wherein an element containing a one-conductivity type semiconductor layer which is in contact with an insulator and an element containing similar semiconductor layer which is not in contact with the insulator are provided in the same semiconductor IC device.

CONSTITUTION: A part A1 equipped with the circuit which requires high speed action is formed by walled system and a part B2 equipped with the circuit which requires high withstand voltage by non-walled system. This manner can reduce the element area because of the formation of the A1 part through walled system and enables high speed action by the increase in integration degree. Since on the other hand the part B2 that requires high withstand voltage is formed by non- walled system, a withstand voltage sufficiently enduring the required withstand voltage can be obtained without the influence of stress under a thick oxide film. Therefore, the titled deivce which can satisfy two requirements, i.e. high withstand voltage and high speed can be obtained.