PURPOSE: To implement low costs and mass production, by providing mirror surfaces on the surface of the diaphragm of a pressure transducing substrate and on the wall surface which is continued to the diaphragm, providing a rough surface with a specific value or less only on the bonding surface with a fixing plate, and soldering the substrates through an Ni player.

CONSTITUTION: An Si3N4 mask 15' is provided on an Si substrate 17 having a diffused resistor layer 13. Etching is performed by KOH. The surfaces of a diaphragm 12 and a side wall 12' are made to be mirror surfaces. A rough surface with #2,000 rough or less is formed on bonding surfaces 18' and 18" of a base substrate 18. The surface of the substrate 17 is protected by wax 21. When nonelectrolytic Ni plating is applied to both substrates, Ni is plated only on the rough surfaces 15', 18' and 18", but it is not plated on the Si on the mirror surfaces. The solder paste 22 is printed through a screen. Then the substrates 17 and 18 are made to face each other and heated in a vacuum. They are bonded, with a hermetically sealed vacuum state 23 being maintained. In this constitution, the rise up of the solder 22 is prevented. The bonded substrates are cut and a pressure sensitive element is completed. In this method, the mass production and the cost reduction of an absolute pressure sensor having a vacuum chamber can be implemented.