SUBSTRATE FOR MOUNTING ELEMENT, MANUFACTURING METHOD OF SUBSTRATE FOR MOUNTING ELEMENT, SEMICONDUCTOR MODULE, AND MANUFACTURING METHOD OF SEMICONDUCTOR MODULE

PROBLEM TO BE SOLVED: To improve connection reliability between a projection structure and an electrode of a semiconductor element in a structure connecting the projection structure and the electrode of the semiconductor element.SOLUTION: An element mounting substrate 10 comprises: an insulating resin layer 12; a wiring layer 14 provided on one main surface of the insulating resin layer 12; and a projection electrode 16 which is electrically connected to the wiring layer 14 and projects from the wiring layer 14 toward the insulating resin layer 12 side. Unevenness is formed on a side surface of the projection electrode 16, and the side surface of the projection electrode 16 is larger in surface roughness than a top surface of the projection electrode 16.