Double-side process silicon MOS and passive devices for RF front-end modules

1. A method for forming integrated circuit, comprising:

providing a first semiconductor substrate having a front surface and a back surface that is opposite to the front surface;

forming one or more first trenches in the first semiconductor substrate from the front surface side, the first trenches being characterized by a first depth;

forming one or more second trenches in the first semiconductor substrate from the front surface side, the second trenches being characterized by a second depth which greater than the first depth;

forming a horizontal isolation layer parallel to the front surface and at a third depth from the front surface;

forming a first recessed region extending in the first semiconductor substrate from the back surface side to the horizontal isolation layer that results in a thinned semiconductor region having a thickness substantially equal to the third depth; and

forming a bulk dielectric layer covering the back surface side of the first semiconductor substrate.

2. The method of claim 1 , wherein forming the first recessed region comprises:

bonding a second substrate on top of the first surface of first substrate;

thinning the backside of the first substrate; and

etching the backside semiconductor to form the first recessed region to expose the horizontal isolation layer.

3. The method of claim 2 , wherein thinning the backside of the first substrate comprises etch the backside of the substrate to expose a bottom portion of the one or more of the second trenches to form a first active region isolated by dielectrics on the sides and at the bottom.

4. The method of claim 3 , further comprising forming a laterally-diffused MOS transistor in the first active region.

5. The method of claim 2 , wherein the bulk dielectric layer includes a first protruding portion extending into the first recessed region, and wherein first protruding portion of the bulk dielectric layer is in contact with the one or more first trenches in the thinned semiconductor region to form a second active region isolated by dielectrics on the sides and at the bottom.

6. The method of claim 5 , further comprising forming a fully depleted semiconductor on insulator (SOI) transistor in the second active region.

7. The method of claim 2 , further comprising:

forming a second recessed region in the first semiconductor substrate from the back surface side, wherein the second recessed region extends to the front surface.

8. The method of claim 7 , wherein the bulk dielectric layer includes a second protruding portion extending into the second recessed region, wherein the method further comprises forming one or more conductive vias through the second protruding portion of the bulk dielectric layer.

9. The method of claim 8 , further comprising forming one or more of an integrated capacitor and an integrated inductor disposed on the second surface side of the substrate.

10. The method of claim 9 , further comprising forming an interconnect structure for coupling the one or more of the integrated capacitor and the integrated inductor to a component on the first surface side of the substrate through one or more conductive vias disposed in the second protruding portion of the bulk dielectric layer.

11. The method of claim 8 , further comprising forming one or more MEMS (micro-mechanical-electrical-system) devices disposed on the second surface side of the substrate.

12. The method of claim 11 , further comprising forming an interconnect structure for coupling the one or more of the MEMS devices to a component on the first surface side of the substrate through one or more conductive vias disposed in the second protruding portion of the dielectric layer.