This invention relates to a method for producing group IB-IIIA-VIA quaternary or higher alloy semiconductor films wherein the method comprises the steps of (i) providing a metal film comprising a mixture of group IB and group IIIA metals; (ii) heat treating the metal film in the presence of a source of a first group VIA element (said first group VIA element hereinafter being referred to as VIA1) under conditions to form a first film comprising a mixture of at least one binary alloy selected from the group consisting of a group IB-VIA1 alloy and a group IIIA-VIA1 alloy and at least one group IB-IIIA-VIA1 ternary alloy (iii) optionally heat treating the first film in the presence of a source of a second group VIA element (said second group VI element hereinafter being referred to as VIA2) under conditions to convert the first film into a second film comprising at least one alloy selected from the group consisting of a group IB-VIA1-VIA2 alloy and a group IIIA-VIA1-VIA2 alloy; and the at least one group IB-III-VIA1 ternary alloy of step (ii); (iv) heat treating either the first film or second film to form a group IB-IIIA-VIA quaternary or higher alloy semiconductor film.