MANUFACTURE OF DEVICE

PROBLEM TO BE SOLVED: To manufacture an integrated circuit device for isolating devices from each other, by a method wherein both of a noise-sensitive element and a noise-generating element are formed on the same single crystal silicon substrate. SOLUTION: A noise-sensitive element is isolated from a noise-generating element by a porous silicon region 12 formed on a substrate 10. The volume of the region 12 depends upon the degree of a necessary isolation of the noise- sensitive element from the noise-generating element. The noise-sensitive element is an analog element and the noise-generating element is a digital element. The substrate 10 is normally a silicon substrate. A diagram when viewed from above of the substrate 10 having an insulating region 12 in the interior thereof for isolating circuit blocks 14 from each other is shown in the diagram. When a mask is formed, the isolation region 12 is formed on the substrate 10 by converting an exposed silicon region into the porous silicon region. The porous silicon region is normally formed by performing an anode etching on the exposed silicon region in a concentrated hydrofluoric acid solution. An insulating substrate 12 is formed so as to pass through the substrate 10, and an analog device is isolated from a digital device.