A nitride crystal is characterized in that, in connection with plane spacing of arbitrary specific parallel crystal lattice planes of the nitride crystal obtained from X-ray diffraction measurement performed with variation of X-ray penetration depth from a surface of the crystal while X-ray diffraction conditions of the specific parallel crystal lattice planes are satisfied, a uniform distortion at a surface layer of the crystal represented by a value of |d.sub.1d.sub.2|/d.sub.2 obtained from the plane spacing d.sub.1 at the X-ray penetration depth of 0.3 m and the plane spacing d.sub.2 at the X-ray penetration depth of 5 m is equal to or lower than 2.110.sup.3. The above configuration provides the nitride crystal having a crystal surface layer that is evaluated directly and reliably without breaking the crystal so that it can be used in a preferred fashion as a substrate for a semiconductor device as well as the nitride crystal substrate, an epilayer-containing nitride crystal substrate, a semiconductor device and a method of manufacturing the same.

A nitride crystal is characterized in that, in connection with plane spacing of arbitrary specific parallel crystal lattice planes of the nitride crystal obtained from X-ray diffraction measurement performed with variation of X-ray penetration depth from a surface of the crystal while X-ray diffraction conditions of the specific parallel crystal lattice planes are satisfied, a uniform distortion at a surface layer of the crystal represented by a value of |d.sub.1d.sub.2|/d.sub.2 obtained from the plane spacing d.sub.1 at the X-ray penetration depth of 0.3 m and the plane spacing d.sub.2 at the X-ray penetration depth of 5 m is equal to or lower than 2.110.sup.3. The above configuration provides the nitride crystal having a crystal surface layer that is evaluated directly and reliably without breaking the crystal so that it can be used in a preferred fashion as a substrate for a semiconductor device as well as the nitride crystal substrate, an epilayer-containing nitride crystal substrate, a semiconductor device and a method of manufacturing the same.

A polyethylene fiber characterized by having an intrinsic viscosity [] of 0.8 dL/g or more and less than 5 dL/g; being composed of a repeating unit substantially derived from ethylene; having pores formed inside of the fiber; having an average diameter of the pores of ranging from 3 nm to 1 m when the diameter is measured, by each pore being approximated by a column, at a contact angle of 140 degrees, in a mercury intrusion method; a porosity of the pores of ranging from 1.5% to 20%; and having a tensile strength greater than or equal to 8 cN/dtex.