Polymerized materials for forming the underfill and encapsulation structures for semiconductor package are disclosed. A filler constituent, such as boron nitride, silicates, elemental metals, or alloys, may be added to a liquid photopolymer resin to tailor the physical properties thereof upon curing. The filler constituents may be employed to alter the coefficient of thermal expansion, thermal conductivity, or electrical conductivity of the polymerized material. A number of different embodiments are disclosed that employ the above materials in selected regions of the underfill and encapsulation structures of the semiconductor package. The polymerized materials may also be used to form support structures and covers for optically interactive semiconductor devices. Methods for forming the above structures using stereolithography are also disclosed.