Patent ID: 7427797

Claim:
A semiconductor device having a surface MEMS element, comprising: a semiconductor substrate; and an actuator which is arranged above the semiconductor substrate via a space and has a lower electrode, an upper electrode, and a piezoelectric layer sandwiched between the lower electrode and the upper electrode, at least an entire surface of the piezoelectric layer being substantially flat; a first electrode layer which is formed on the semiconductor substrate, and a second electrode layer which is arranged above the semiconductor substrate via the space, opposes the first electrode layer, and moves in accordance with movement of the actuator, and in which the first electrode layer and the second electrode layer function as a variable capacitor when a distance between the first electrode layer and the second electrode layer changes in accordance with the movement of the actuator, wherein the semiconductor substrate has a first region and a second region, the variable capacitor is formed in the first region, a first transistor having a first gate electrode and first source and drain diffusion layers is formed in the second region, the first electrode layer is made of a same material as the first gate electrode, the first electrode layer is provided above an insulation region in the first region of the semiconductor substrate, and a first well layer of a first conductivity type surrounds the first source and drain diffusion layers in the second region and is not provided below the first electrode layer.