Multilayered circuit board and semiconductor device

1. A multilayered circuit board having a single-side laminated structure, the multilayered circuit board which does not include a core substrate having via-holes formed therethrough and vias for providing electrical connection through the via-holes, comprising:

a plurality of pairs of layers, each pair including a conductor circuit layer and an insulator layer,

wherein a glass transition temperature of each insulator layer is 170° C. or higher, a coefficient of thermal expansion at the glass transition temperature or lower of each insulator layer is 35 ppm or less, and a modulus of elasticity of each insulator layer is 5 GPa or more,

wherein the insulator layer includes at least a first resin layer, a second resin layer, and a fiber base member provided between the first and second resin layers, and

wherein when a thickness of the first resin layer is defined as “B 1 ” and a thickness of the second resin layer is defined as “B 2 ”, B 1 and B 2 satisfy 0<B 2 /B 1 ≦1.

2. The multilayered circuit board as claimed in claim 1 , wherein a thickness of the fiber base member included in the insulator layer is in the range of 10 to 35 mu.m.

3. The multilayered circuit board as claimed in claim 1 , wherein the fiber base member is a glass cloth.

4. The multilayered circuit board as claimed in claim 1 , wherein the insulator layer is formed of a resin composition containing cyanate resin.

5. A semiconductor device in which the multilayered circuit board defined by claim 1 is used.