A method for forming capacitor is proposed. The key point of the invention is that bottom plate and dielectric layer of capacitor are formed before metal interconnect is formed. Thus, thermal treatment of dielectric layer does not affect metal interconnect. Therefore, conventional fault that quality of dielectric layer is degraded by scant annealing is avoided, and then dielectric layer and metal interconnect can be optimized respectively. Obviously, the ultimate advantage of the proposed method is that not only breakdown voltage of dielectric layer is increased by annealing but also quality of metal interconnect is not affected by annealing. Therefore, an incidental advantage of the proposed method is that the method is beneficial to form both capacitor and metal interconnect.

According to one embodiment of the invention, a method for fabricating a MIM capacitor in a semiconductor die includes a step of depositing a first interconnect metal layer. The method further includes depositing a layer of silicon nitride on the first interconnect layer. The layer of silicon nitride is deposited in a deposition process using an ammonia-to-silane ratio of at least 12.5. The method further includes depositing a layer of MIM capacitor metal on the layer of silicon nitride. The method further includes etching the layer of MIM capacitor metal to form an upper electrode of the MIM capacitor. According to this exemplary embodiment, the method further includes etching the layer of silicon nitride to form a MIM capacitor dielectric segment and etching the first interconnect metal layer to form a lower electrode of the MIM capacitor. The MIM capacitor has a capacitance density of at least 2.0 fF/um.sup.2.

A semiconductor wafer has a dielectric layer. A bottom plate recess is first formed in the dielectric layer, and a metal bottom plate is formed in the bottom plate recess. An insulation layer is formed on the metal bottom plate, and a via hole is formed in the insulation layer. A first metal layer is then formed on the insulation layer that fills the via hole so as to form a via plug. Finally, a metal upper plate is formed on the insulation layer, and a metal wire is formed on top of the via plug.

A lower metal layer is provided on a lower interlayer insulating film in an MIM capacitance element forming region. The lower metal layer is formed by the same step as that in which the lower interconnection layer is formed. A dielectric layer and an upper metal layer patterned using the same mask are provided on the lower metal layer. The upper metal layer is formed to have a thickness that is thinner than the thickness of the lower metal layer. Thus, it becomes possible to achieve high reliability (lifetime) of the MIM capacitance element by improving the structure of the MIM capacitance element as well as the manufacturing steps.

A semiconductor device having a capacitor and a method of manufacturing thereof are provided, securing a certain capacitance while allowing the size to be reduced. The semiconductor device includes a capacitor lower electrode having an upper surface and including a metal film, a dielectric film deposited on the upper surface of the capacitor lower electrode and having its thickness smaller than that of the capacitor lower electrode, and a capacitor upper electrode deposited on the dielectric film, having its width smaller than that of the capacitor lower electrode and including a metal film.