Disclosed is a method for mounting a semiconductor element, the method requiring no strict flatness for a substrate and being reliable in a semiconductor device produced by mounting a semiconductor element on a circuit substrate. In the multilayer circuit substrate comprising bump electrodes formed of a conductive paste, a conductive adhesive is applied to the top of bump electrodes and then leveled to obtain the end portions on the bump electrodes with a high coplanarity in height. The semiconductor element is mounted on this substrate using a combination of a conductive resin and a sealing resin or an anisotropic conductive sheet. Every top of the bump electrodes after the conductive adhesive is applied has a high coplanarity. The semiconductor element can be mounted with high reliability, on the substrate having such a poor flatness of the electrode face that mounting by a conventional method can not be applied.