JP3521921B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a semiconductor device having a buried contact layer, and more particularly to a structure of an element isolation region. 2. Description of the Related Art FIG. 3 shows a structure of a conventional MOSFET having a buried contact layer. P-type semiconductor substrate 1
On the surface, an N-channel MOSF composed of source and drain regions composed of an N-type impurity diffusion layer 2, a gate oxide film 3, and a gate electrode 4 composed of a polycrystalline silicon film.
ET is formed. Element isolation film 9 adjacent to buried contact layer 6 formed by polycrystalline silicon film 5
Is the same as the isolation width of the element isolation film 7 not adjacent to the buried contact layer 6 (L2 in the figure). [0003] However, the semiconductor device having the conventional structure as described above has the following problems. In order to contact a silicon substrate with a polycrystalline silicon film and to form a buried contact layer made of an impurity layer diffused from the polycrystalline silicon film, a silicon substrate must be formed before the polycrystalline silicon film is formed. It is necessary to remove the silicon oxide film. At this time, since patterning for removal is performed in consideration of misalignment in the photolithography process, a part of the element isolation film adjacent to the buried contact layer is also removed. The removal of the device isolation film reduces the film thickness of the device isolation film and further reduces the device isolation width, thereby deteriorating the device isolation characteristics and easily forming a parasitic MOS transistor. Accordingly, the present invention is to solve such a problem, and an object of the present invention is to provide a semiconductor device having a buried contact layer and having improved element isolation characteristics. It is in. A method for manufacturing a semiconductor device according to the present invention is a method for manufacturing a semiconductor device having a MOS transistor including a buried contact layer, wherein a first LOCOS film is formed on a semiconductor substrate. Forming a second LOCOS film wider than the first LOCOS film; and forming a gate insulating film on the semiconductor substrate sandwiched between the first LOCOS film and the second LOCOS film. Forming and forming an opening in the gate insulating film by removing a portion of the gate insulating film close to the second LOCOS film and an upper portion of the second LOCOS film. Forming a conductor layer in the opening, and burying the embedded contact layer in the semiconductor substrate below the opening from the conductor layer to the substrate below the opening. Forming an impurity by introducing an impurity, and forming a first impurity region to be one of a source region and a drain region of the MOS transistor in a region adjacent to the buried contact layer;
Forming a second impurity region serving as the other of the source region and the drain region in a region adjacent to the OS film, wherein the second L region adjacent to the buried contact layer is formed.
A semiconductor device in which the width of the OCOS film is wider than the width of the first LOCOS film is obtained. An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a structural sectional view of a semiconductor device according to the present invention. On the surface of a P-type semiconductor substrate 1, a source / drain region comprising an N-type impurity diffusion layer 2 and a gate oxide film 3
And an N-channel MOSFET formed by a gate electrode 4 made of a polycrystalline silicon film.
Isolation width of element isolation film 9 adjacent to buried contact layer 6 formed by polycrystalline silicon film 5 (L1 in the figure)
Is a device isolation film 7 not adjacent to the buried contact layer 6
(L2 in the figure). Next, one embodiment of a method of manufacturing a semiconductor device according to the present invention will be described with reference to FIGS. 2 (a) to 2 (d). First, an element isolation film 10 and a gate oxide film 3 of about 200 Å are formed on the surface of a P-type semiconductor substrate 1. This state is shown in FIG. Next, using the patterned photoresist film 8, the gate oxide film 3 in the region where the buried contact layer is to be formed is removed. At this time, the upper portion of the element isolation film 9 in the region adjacent to the buried contact layer is also removed at the same time. This state is shown in FIG. Next, after removing the photoresist film, about 40
A polycrystalline silicon film of 00 Å is formed by a chemical vapor deposition method, and an N-type impurity, for example, phosphorus ions is ion-implanted and then patterned to form a MOSFET gate electrode 4 and a buried contact layer. A silicon film 5 is formed. Next, 800-900 ° C
By thermal annealing to a certain extent, phosphorus in the polycrystalline silicon film 5 is introduced into the P-type semiconductor substrate 1 from the opening of the gate oxide film 3 to form a buried contact layer 6. This state is shown in FIG. Next, the gate electrode 4, the polycrystalline silicon film 5
And an N-type impurity using the element isolation films 7 and 9 as a mask.
For example, phosphorus ions are implanted, and the N-type impurity diffusion layer 2 is formed.
To form This state is shown in FIG. Thereafter, a semiconductor device having a buried contact layer can be obtained by an ordinary process. The above has been specifically described based on the embodiments.
The present invention is not limited to the above embodiment. For example, the present invention can be applied even if the MOSFET is a P-channel type. As described above, according to the present invention, in a semiconductor device having a buried contact layer, the isolation width of an element isolation film adjacent to the buried contact layer is reduced by an element not adjacent to the buried contact layer. By making the separation width larger than the separation width of the separation film, it is possible to prevent the deterioration of the element separation characteristics due to the removal of the element separation film due to the formation of the buried contact layer, and to provide a semiconductor device with improved element separation characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a structural sectional view of a semiconductor device of the present invention. FIG. 2 is a view showing one embodiment of a method of manufacturing a semiconductor device according to the present invention. FIG. 3 is a diagram showing a structural cross-sectional view of a conventional semiconductor device. [Description of Signs] 1 P-type semiconductor substrate 2 N-type impurity diffusion layer 3 gate oxide film 4 gate electrode 5 polycrystalline silicon film 6 buried contact layer 7 element isolation film 8 not in contact with buried contact layer 8 photoresist film 9 buried contact layer Isolation film 10 in contact with device Isolation film

   ────────────────────────────────────────────────── ─── Continuation of front page       (56) References JP-A-3-114254 (JP, A)                 JP-A-62-57228 (JP, A)                 JP-A-59-75653 (JP, A)                 JP-A-63-200562 (JP, A)                 JP-A-3-187224 (JP, A)

Claims (1)

(57) A method of manufacturing a semiconductor device having a MOS transistor including a buried contact layer, wherein a first LOCOS film and a first LOCOS film are formed on a semiconductor substrate.
Forming a second LOCOS film wider than the S film; and forming a gate insulating film on the semiconductor substrate sandwiched between the first LOCOS film and the second LOCOS film Forming a hole in the gate insulating film by removing a portion of the gate insulating film close to the second LOCOS film and an upper part of the second LOCOS film; Forming a conductor layer in the opening; and introducing the buried contact layer into the semiconductor substrate below the opening from the conductor layer into the substrate below the opening. Forming the MOS transistor in a region adjacent to the buried contact layer.
Forming a first impurity region to be either a source region or a drain region of the transistor;
Forming a second impurity region serving as the other of the source region and the drain region in a region adjacent to a COS film, wherein the second LOC adjacent to the buried contact layer is provided.
A method for manufacturing a semiconductor device, comprising: obtaining a semiconductor device having an OS film having a width larger than that of the first LOCOS film.