Abstract: A semiconductor integrated circuit device includes a high voltage circuit and a high-speed signal processing circuit on the same chip. The high-speed signal processing circuit is made to have a stacked construction thereby to reduce the power consumption. It is also surrounded by ground potential lines so that it may be prevented from being adversely affected by a high voltage used in the high voltage circuit. Each of the high voltage elements composing the high voltage circuit has its principal surface formed at its base and collector regions with guard ring layers of the same conduction types as the respective ones of the high voltage elements. The guard ring layers extend over the elements and the semiconductor body and have lower impurity concentrations than the respective ones of the elements.