Method of manufacturing a semiconductor device and semiconductor device obtained by means of said method
The invention relates to a method of manufacturing a semiconductor device comprising a substrate ( 1 ) and a semiconductor body ( 2 ) in which at least one semiconductor element is formed, wherein, in the semiconductor body ( 2 ), a semiconductor island ( 3 ) is formed by forming a first cavity ( 4 ) in the surface of the semiconductor body ( 2 ), the walls of said first cavity being covered with a first dielectric layer ( 6 ), after which, by means of underetching through the bottom of the cavity ( 4 ), a lateral part of the semiconductor body ( 2 ) is removed, thereby forming a cavity ( 20 ) in the semiconductor body ( 2 ) above which the semiconductor island ( 3 ) is formed, and wherein a second cavity ( 5 ) is formed in the surface of the semiconductor body ( 2 ), the walls of said second cavity being covered with a second dielectric layer, and one of the walls covered with said second dielectric layer forming a side wall of the semiconductor island ( 3 ). According to the invention, the same dielectric layer ( 6 ) is chosen for the first and the second dielectric layer, a lateral size of the second cavity ( 5 ) and the thickness of the dielectric layer ( 6 ) are chosen such that the second cavity ( 5 ) becomes nearly completely filled by the dielectric layer ( 6 ), and the lateral sizes of the first cavity ( 4 ) are chosen such that the walls and the bottom of the first cavity ( 4 ) are provided with a uniform coating by the dielectric layer ( 6 ). In this way, a semiconductor island ( 3 ) which is isolated from its environment can be made using a minimum number of (masking) steps.
1. A method of manufacturing a semiconductor device comprising a substrate and a semiconductor body in which at least one semiconductor element is formed, wherein, in the semiconductor body, a semiconductor island is formed by forming, in the surface of the semiconductor body, a first recess the walls of which are covered with a dielectric layer ( 6 ), after which a lateral part of the semiconductor body is removed by means of underetching via the bottom of the first recess, thereby forming a cavity in the semiconductor body above which the semiconductor island is formed, and wherein a second recess is formed in the surface of the semiconductor body, the walls of said second recess being covered with the dielectric layer, and one of the walls of the second recess covered with the dielectric layer being used to form a side wall of the semiconductor island, characterized in that a lateral dimension of the second recess and the thickness of the dielectric layer being chosen such that the second recess is filled substantially completely by the dielectric layer, and the lateral dimensions of the first recess being chosen such that the walls and the bottom of the first recess are provided with a uniform coating by the dielectric layer.
2. A method as claimed in claim 1 , characterized in that after the formation of the first and the second recesses, the dielectric layer is applied over the entire surface of the semiconductor body, after which the flat parts of the dielectric layer are removed by means of anisotropic etching.
3. A method as claimed in claim 1 , characterized in that the second recess is formed as a ring-shaped groove surrounding the first recess, within which groove the semiconductor island is formed, the lateral dimension of the second recess being formed by the width of the groove.
4. A method as claimed in claim 1 , characterized in that before the dielectric layer is provided, grooves are formed in the surface of the semiconductor body, which have approximately the same width as the second recess, as a result of which the semiconductor island is divided into semiconductor sub-islands.
5. A method as claimed in claim 4 , characterized in that the shape of the second recess, viewed in projection, is square, and the grooves are formed so as to extend from the middle of the sides of the square to the first recess situated in the center.
6. A method as claimed in claim 1 ,characterized in that the semiconductor body is formed by a semiconductor substrate on which first and second semiconductor layers, which are formed of different semiconductor materials, are provided.
7. A method as claimed in claim 6 , characterized in that the first semiconductor layer of a mixed crystal of silicon and germanium is provided on the semiconductor substrate, and the second semiconductor layer of silicon is provided on the first semiconductor layer.
8. A method as claimed in claim 6 , characterized in that to form the cavity in the semiconductor body use is made of an etchant for silicon which is selective with respect to the semiconductor material of the first semiconductor layer.
9. A method as claimed in claim 8 , characterized in that after the formation of the cavity, the first semiconductor layer is removed by means of an etchant which is selective with respect to the semiconductor material of the second semiconductor layer.
10. A method as claimed in claim 8 , characterized in that during the formation of the cavity, the etching of silicon is stopped as soon as the cavity has reached the first semiconductor layer, after which the first semiconductor layer is selectively removed.
11. A method as claimed in claim 1 , characterized in that a lateral dimension of the cavity is chosen to be so large that the cavity in the semiconductor body extends, in this lateral direction, at least as far as the second recess.
12. A method as claimed in claim 1 , characterized in that, in the semiconductor body, a further layer is formed from a different semiconductor material than the part of the semiconductor body ( 2 ) in which the cavity is formed.
13. A method as claimed in claim 1 , characterized in that after the formation of the cavity, the walls thereof are covered with a different dielectric layer.
14. A method as claimed in claim 13 , characterized in that the cavity is filled with polycrystalline silicon after the walls of the cavity are covered with the different dielectric layer.
15. A method as claimed in claim 1 , characterized in that after the formation of the cavity, this cavity is filled with a high-ohmic material.