Abstract: A semiconductor device, which can easily form hyper abrupt junction type junction having a desired depletion layer width or transition region width, is disclosed. A silicon oxide film is formed on the mirror polished side surface of a P-type semiconductor substrate. Then, a P-type diffusion layer is formed by means of heat treatment. In this process, impurity concentration distribution is formed in such a way that the impurity concentration distribution can abruptly decrease from the mirror polished side surface of the substrate. Following this, the oxide film is removed by etching, and hyper abrupt type PN junction is obtained by sticking the mirror polished side surface of a high impurity concentration N-type semiconductor substrate and the high impurity concentration diffusion side of the above P-type semiconductor substrate to each other in the same surface direction as that of the above P-type semiconductor substrate.

Abstract: A filter which can operate as a digital filter of the finite impulse response type or the infinite impulse response type using one circuit. The signal to be filtered is multiplied and added using a first calculation circuit and a second calculation circuit. The outputs of the calculation circuits are added using addition circuits. Either the output of the addition circuit or the input of the first calculation circuit is applied by a switching element to the first calculation circuit.