A method for concurrently forming a first metal electrode (31, 58) on an n-type region of a silicon substrate (10) and a second metal electrode (32, 59) on a p-type region of the silicon substrate, wherein the n-type region and the p-type region are respectively exposed in a first and in a second area, is disclosed. The method comprises: depositing (101) an initial metal layer comprising Ni (33, 53) simultaneously in the first area and in the second area by a Ni immersion plating process using a plating solution; and depositing (102) a further metal layer (34, 54) on the initial metal layer comprising Ni (33, 53) in the first area and in the second area by an electroless metal plating process or by an immersion metal plating process, wherein the plating solution comprises Ni and a predetermined amount of another metal different from Ni.