Contact structure for connecting an electrode to a semiconductor device and a method of forming the same

A method of forming a contact structure for connecting a semiconductor device to a wiring electrode, comprising the steps of:

• depositing a first metal on a surface of a semiconductor layer constituting a part of the semiconductor device to form a first metal layer in contact with the semiconductor layer, said first metal being chosen such that it reacts with the semiconductor layer when annealed;
• annealing the first metal layer at a first temperature to form a first contact layer as a result of reaction between the semiconductor layer and the first metal;
• depositing an insulator material on the first contact layer to form an insulator layer such that the first contact layer is buried under the insulator layer;
• providing a penetrating hole through the insulator layer so as to expose a part of the first contact layer;
• depositing said first metal on the insulator layer in correspondence to the penetrating hole so as to cover at least said part of the first contact layer exposed by the penetrating hole to form a second metal layer;
• annealing at a second temperature higher than the first temperature to form a second contact layer as a result of reaction due to the second temperature between the first metal of the second metal layer and the semiconductor layer through the first contact layer;
• and depositing the wiring electrode on the second metal layer.