The phenomenon that a common positive photoresist (PR) releases nitrogen (N2) gas when exposed to UV light has never been used or received any particular attention. Fabrication process to intentionally trap the generated N2 gas during UV exposure, thereby, to form the microcavity structure is proposed. Various dome-shaped structures are demonstrated with the proposed process. This process is best suited to make various cavity packages in microelectromechanical systems. Also, microlens arrays are fabricated using plastic replication of the dome-shaped microcavities. All these results lead to a different view of the conventional positive photoresist and inspire various new applications.