Provided herein is a method including bonding a first oxide layer on a handle substrate to a second oxide layer on a complementary metal oxide semiconductor (“CMOS”), wherein the fusion bonding forms a unified oxide layer including a diaphragm overlying a cavity on the CMOS. The handle substrate is removed leaving the unified oxide layer. A piezoelectric film stack is deposited over the unified oxide layer. Vias are formed in the piezoelectric film stack and the unified oxide layer. An electrical contact layer is deposited, wherein the electrical contact layer electrically connects the piezoelectric film stack to an electrode on the CMOS.