Silicon film bulk acoustic wave device and process of the same

A film bulk acoustic wave device, comprising:

• a silicon substrate;
• an oxidation protective film or etch protecting film formed in a pattern of dividing a resonance region to form an acoustic reflective layer on the silicon substrate;
• a thermal oxidation film formed by partially thermally oxidizing the silicon substrate in an electrode region where the oxidation protective film or etch protecting film is not formed;
• and
• a lower electrode, a piezoelectric thin film and an upper electrode on the thermal oxidation film.

A method of manufacturing a film bulk acoustic wave device, comprising the steps of:

• forming a sacrificial layer of Poly-Si or Si on a substrate;
• forming a thermal oxidation film by oxidizing the sacrificial layer in portions except for a portion where the acoustic reflective layer is to be formed;
• forming an etch protecting film of silicon oxide or silicon nitride on the sacrificial layer in a predetermined thickness;
• forming a lower electrode by depositing a conductive material in a predetermined pattern on the etch protecting film and the thermal oxidation film;
• forming a piezoelectric thin film by depositing a material with a piezoelectric characteristic in a predetermined pattern on the lower electrode and the thermal oxidation film;
• and
• forming an upper electrode by depositing a conductive material in a predetermined pattern on the piezoelectric thin film.

A method of manufacturing a film bulk acoustic wave device, comprising the steps of:

• forming a thermal oxidation film on a silicon substrate by oxidizing the substrate in portions except for a portion where the acoustic reflective layer is to be formed;
• forming an etch protecting film of silicon oxide or silicon nitride on the silicon substrate in a predetermined thickness;
• forming a lower electrode by depositing a conductive material in a predetermined pattern on the etch protecting film and the thermal oxidation film;
• forming a piezoelectric thin film by depositing a material with piezoelectric characteristics in a predetermined pattern on the lower electrode and the thermal oxidation film;
• and
• forming an upper electrode by depositing a conductive material in a predetermined pattern on the piezoelectric thin film.

A method of manufacturing a film bulk acoustic wave device, comprising the steps of:

• forming a sacrificial layer of Poly-Si or Si on a substrate;
• forming a lower electrode by depositing a conductive material in a predetermined pattern on the sacrificial layer;
• forming a piezoelectric thin film by depositing a material with piezoelectric characteristics in a predetermined pattern on the lower electrode and a thermal oxidation film;
• forming an upper electrode by depositing a conductive material in a predetermined pattern on the piezoelectric thin film;
• forming a lower electrode/piezoelectric layer/upper electrode and then cutting and separating the substrate for each film bulk acoustic wave device;
• and
• forming an acoustic reflective layer as an empty space by removing the sacrificial layer for each cut and separated film bulk acoustic wave device.