PURPOSE: To enhance the convolution efficiency, to make the temperature characteristic, as well satisfactory, and to improve the yield of manufacture by forming an Si epitaxial layer in a monolithic SAW convolver structure by a GaAs epitaxial layer.

CONSTITUTION: The convolver contains a high concentration Si substrate 11, a GaAs epitaxial layer 12 formed on the substrate, an insulator 21 formed on the epitaxial layer, a piezoelectric film 3 formed on the insulator, an input transducer 7 formed so as to come into contact with the piezoelectric film and an output gate 8. Accordingly, as for GaAs used for the epitaxial layer of an SAW convolver structure, its mobility is larger than several folds of the mobility of Si, therefore, a loss in the epitaxial layer can be made smaller than a conventional structure, the convolution efficiency can be improved and the temperature characteristic can be improved. In such a way, a satisfactory convolution efficiency is obtained, and also, the temperature characteristic is satisfactory, and moreover, the yield of structure can be improved.