Semiconductor device

1. A semiconductor device comprising:

a substrate;

a first insulator formed in a first area of the substrate, and a second insulator formed in a second area of the substrate;

a first transistor formed over a first device region surrounded by the first area, the first transistor comprising

a first gate insulating film having a first thickness, the first gate insulating film being formed over the first device region,

a first gate electrode formed over the first gate insulating film, and

first source and drain regions formed in the first device region at both sides of the first gate electrode;

a second transistor formed over a second device region surrounded by the second area, the second transistor comprising

a second gate insulating film formed over the second device region, the second gate insulating film having a second thickness less than the first thickness of the first gate insulating film,

a second gate electrode formed over the second gate insulating film, and

second source and drain regions formed in the second device region at both sides of the second gate electrode;

a third insulator formed in a third area of the substrate; and

a memory cell formed over a third device region surrounded by the third area, the memory cell further comprising

a tunnel insulating film formed over the third device region,

a floating gate formed over the tunnel insulating film,

an insulating film formed over the floating gate,

a control gate formed over the tunnel insulating film, and

third source and drain regions formed in third device region at both sides of the floating gate and the control gate;

wherein a first height of a top surface of the first insulator is less than a second height of a top surface of the second insulator, and

wherein the first height of the top surface of the first insulator is less than a third height of a top surface of the third insulator.

2. The semiconductor device according to claim 1 , further comprising:

a fourth insulator formed in a fourth area of the substrate; and

a third transistor formed over a fourth device region surrounded by the fourth area, the third transistor further comprising

a fourth gate insulating film formed over the fourth device region, the fourth gate insulating film having a third thickness greater than the first thickness of the first gate insulating film,

a third gate electrode formed over the fourth gate insulating film, and fourth source and

drain regions formed in the fourth device region at both sides of the electrode.

3. The semiconductor device according to claim 1 , wherein the second height of the top surface of the second insulator is less than the height of the top surface of the third insulator.