An I.sup.2 L semiconductor device in which a p-type buried layer is formed on an n.sup.+ type silicon substrate by diffusion of boron, an epitaxial n-type layer is grown on the p-type buried layer, a p.sup.+ type region is formed in a ring shape to surround the epitaxial n-type layer with the bottom of the p.sup.+ region reaching to the p-type buried layer, an n-type resistor layer is formed in the epitaxial n-type layer by diffusion of phosphorus, and connections for electrodes are formed by diffusion of n.sup.+ type impurities in such a manner that the connections make contact with the resistor layer.